com.xunlei.util.DateUtils.java Source code

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.xunlei.util;

import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.TimeZone;
import org.apache.commons.lang.StringUtils;

/**
 * <p>
 * A suite of utilities surrounding the use of the {@link java.util.Calendar} and {@link java.util.Date} object.
 * </p>
 * <p>
 * DateUtils contains a lot of common methods considering manipulations of Dates or Calendars. Some methods require some extra explanation. The truncate, ceiling and round methods could be considered
 * the Math.floor(), Math.ceil() or Math.round versions for dates This way date-fields will be ignored in bottom-up order. As a complement to these methods we've introduced some fragment-methods. With
 * these methods the Date-fields will be ignored in top-down order. Since a date without a year is not a valid date, you have to decide in what kind of date-field you want your result, for instance
 * milliseconds or days.
 * </p>
 * 
 * @author Apache Software Foundation
 * @author <a href="mailto:sergek@lokitech.com">Serge Knystautas</a>
 * @author Janek Bogucki
 * @author <a href="mailto:ggregory@seagullsw.com">Gary Gregory</a>
 * @author Phil Steitz
 * @author Robert Scholte
 * @since 2.0
 * @version $Id: DateUtils.java 911986 2010-02-19 21:19:05Z niallp $
 */
public class DateUtils {

    /**
     * The UTC time zone (often referred to as GMT).
     */
    public static final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone("GMT");
    /**
     * Number of milliseconds in a standard second.
     * 
     * @since 2.1
     */
    public static final long MILLIS_PER_SECOND = 1000;
    /**
     * Number of milliseconds in a standard minute.
     * 
     * @since 2.1
     */
    public static final long MILLIS_PER_MINUTE = 60 * MILLIS_PER_SECOND;
    /**
     * Number of milliseconds in a standard hour.
     * 
     * @since 2.1
     */
    public static final long MILLIS_PER_HOUR = 60 * MILLIS_PER_MINUTE;
    /**
     * Number of milliseconds in a standard day.
     * 
     * @since 2.1
     */
    public static final long MILLIS_PER_DAY = 24 * MILLIS_PER_HOUR;

    /**
     * This is half a month, so this represents whether a date is in the top or bottom half of the month.
     */
    public final static int SEMI_MONTH = 1001;

    private static final int[][] fields = { { Calendar.MILLISECOND }, { Calendar.SECOND }, { Calendar.MINUTE },
            { Calendar.HOUR_OF_DAY, Calendar.HOUR }, { Calendar.DATE, Calendar.DAY_OF_MONTH, Calendar.AM_PM
            /* Calendar.DAY_OF_YEAR, Calendar.DAY_OF_WEEK, Calendar.DAY_OF_WEEK_IN_MONTH */
            }, { Calendar.MONTH, DateUtils.SEMI_MONTH }, { Calendar.YEAR }, { Calendar.ERA } };

    /**
     * A week range, starting on Sunday.
     */
    public final static int RANGE_WEEK_SUNDAY = 1;

    /**
     * A week range, starting on Monday.
     */
    public final static int RANGE_WEEK_MONDAY = 2;

    /**
     * A week range, starting on the day focused.
     */
    public final static int RANGE_WEEK_RELATIVE = 3;

    /**
     * A week range, centered around the day focused.
     */
    public final static int RANGE_WEEK_CENTER = 4;

    /**
     * A month range, the week starting on Sunday.
     */
    public final static int RANGE_MONTH_SUNDAY = 5;

    /**
     * A month range, the week starting on Monday.
     */
    public final static int RANGE_MONTH_MONDAY = 6;

    /**
     * Constant marker for truncating
     */
    private final static int MODIFY_TRUNCATE = 0;

    /**
     * Constant marker for rounding
     */
    private final static int MODIFY_ROUND = 1;

    /**
     * Constant marker for ceiling
     */
    private final static int MODIFY_CEILING = 2;

    /**
     * <p>
     * <code>DateUtils</code> instances should NOT be constructed in standard programming. Instead, the class should be used as <code>DateUtils.parse(str);</code>.
     * </p>
     * <p>
     * This constructor is public to permit tools that require a JavaBean instance to operate.
     * </p>
     */
    public DateUtils() {
        super();
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Checks if two date objects are on the same day ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 Mar 2002 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @since 2.1
     */
    public static boolean isSameDay(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        return isSameDay(cal1, cal2);
    }

    /**
     * <p>
     * Checks if two calendar objects are on the same day ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 Mar 2002 13:45 would return false.
     * </p>
     * 
     * @param cal1 the first calendar, not altered, not null
     * @param cal2 the second calendar, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either calendar is <code>null</code>
     * @since 2.1
     */
    public static boolean isSameDay(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
                && cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR));
    }

    /**
     * <p>
     * Checks if two date objects are on the same week ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 Mar 2002 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameWeek(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        return isSameWeek(cal1, cal2);
    }

    /**
     * <p>
     * Checks if two calendar objects are on the same week ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 Mar 2002 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameWeek(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
                && cal1.get(Calendar.WEEK_OF_YEAR) == cal2.get(Calendar.WEEK_OF_YEAR));
    }

    /**
     * <p>
     * Checks if two date objects are on the same month ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 April 2002 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameMonth(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        return isSameMonth(cal1, cal2);
    }

    /**
     * <p>
     * Checks if two calendar objects are on the same month ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 April 2002 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameMonth(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
                && cal1.get(Calendar.MONTH) == cal2.get(Calendar.MONTH));
    }

    /**
     * <p>
     * Checks if two date objects are on the same year ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 April 2003 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameYear(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        return isSameYear(cal1, cal2);
    }

    /**
     * <p>
     * Checks if two calendar objects are on the same year ignoring time.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 06:01 would return true. 28 Mar 2002 13:45 and 12 April 2003 13:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameYear(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR));
    }

    /**
     * <p>
     * Checks if two date objects are on the same hour.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 13:01 would return true. 28 Mar 2002 13:45 and 28 Mar 2002 14:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameHour(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar cal1 = Calendar.getInstance();
        cal1.setTime(date1);
        Calendar cal2 = Calendar.getInstance();
        cal2.setTime(date2);
        return isSameHour(cal1, cal2);
    }

    /**
     * <p>
     * Checks if two calendar objects are on the same hour.
     * </p>
     * <p>
     * 28 Mar 2002 13:45 and 28 Mar 2002 13:01 would return true. 28 Mar 2002 13:45 and 28 Mar 2002 14:45 would return false.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same day
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @author Weapon Chung
     * @since 2011-4-2 10:48:50
     */
    public static boolean isSameHour(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
                && cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR)
                && cal1.get(Calendar.HOUR_OF_DAY) == cal2.get(Calendar.HOUR_OF_DAY));
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Checks if two date objects represent the same instant in time.
     * </p>
     * <p>
     * This method compares the long millisecond time of the two objects.
     * </p>
     * 
     * @param date1 the first date, not altered, not null
     * @param date2 the second date, not altered, not null
     * @return true if they represent the same millisecond instant
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @since 2.1
     */
    public static boolean isSameInstant(Date date1, Date date2) {
        if (date1 == null || date2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return date1.getTime() == date2.getTime();
    }

    /**
     * <p>
     * Checks if two calendar objects represent the same instant in time.
     * </p>
     * <p>
     * This method compares the long millisecond time of the two objects.
     * </p>
     * 
     * @param cal1 the first calendar, not altered, not null
     * @param cal2 the second calendar, not altered, not null
     * @return true if they represent the same millisecond instant
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @since 2.1
     */
    public static boolean isSameInstant(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return cal1.getTime().getTime() == cal2.getTime().getTime();
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Checks if two calendar objects represent the same local time.
     * </p>
     * <p>
     * This method compares the values of the fields of the two objects. In addition, both calendars must be the same of the same type.
     * </p>
     * 
     * @param cal1 the first calendar, not altered, not null
     * @param cal2 the second calendar, not altered, not null
     * @return true if they represent the same millisecond instant
     * @throws IllegalArgumentException if either date is <code>null</code>
     * @since 2.1
     */
    public static boolean isSameLocalTime(Calendar cal1, Calendar cal2) {
        if (cal1 == null || cal2 == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        return (cal1.get(Calendar.MILLISECOND) == cal2.get(Calendar.MILLISECOND)
                && cal1.get(Calendar.SECOND) == cal2.get(Calendar.SECOND)
                && cal1.get(Calendar.MINUTE) == cal2.get(Calendar.MINUTE)
                && cal1.get(Calendar.HOUR) == cal2.get(Calendar.HOUR)
                && cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR)
                && cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR)
                && cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA) && cal1.getClass() == cal2.getClass());
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Parses a string representing a date by trying a variety of different parsers.
     * </p>
     * <p>
     * The parse will try each parse pattern in turn. A parse is only deemed successful if it parses the whole of the input string. If no parse patterns match, a ParseException is thrown.
     * </p>
     * The parser will be lenient toward the parsed date.
     * 
     * @param str the date to parse, not null
     * @param parsePatterns the date format patterns to use, see SimpleDateFormat, not null
     * @return the parsed date
     * @throws IllegalArgumentException if the date string or pattern array is null
     * @throws ParseException if none of the date patterns were suitable (or there were none)
     */
    public static Date parseDate(String str, String[] parsePatterns) throws ParseException {
        return parseDateWithLeniency(str, parsePatterns, true);
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Parses a string representing a date by trying a variety of different parsers.
     * </p>
     * <p>
     * The parse will try each parse pattern in turn. A parse is only deemed successful if it parses the whole of the input string. If no parse patterns match, a ParseException is thrown.
     * </p>
     * The parser parses strictly - it does not allow for dates such as "February 942, 1996".
     * 
     * @param str the date to parse, not null
     * @param parsePatterns the date format patterns to use, see SimpleDateFormat, not null
     * @return the parsed date
     * @throws IllegalArgumentException if the date string or pattern array is null
     * @throws ParseException if none of the date patterns were suitable
     * @since 2.5
     */
    public static Date parseDateStrictly(String str, String[] parsePatterns) throws ParseException {
        return parseDateWithLeniency(str, parsePatterns, false);
    }

    /**
     * <p>
     * Parses a string representing a date by trying a variety of different parsers.
     * </p>
     * <p>
     * The parse will try each parse pattern in turn. A parse is only deemed successful if it parses the whole of the input string. If no parse patterns match, a ParseException is thrown.
     * </p>
     * 
     * @param str the date to parse, not null
     * @param parsePatterns the date format patterns to use, see SimpleDateFormat, not null
     * @param lenient Specify whether or not date/time parsing is to be lenient.
     * @return the parsed date
     * @throws IllegalArgumentException if the date string or pattern array is null
     * @throws ParseException if none of the date patterns were suitable
     * @see java.util.Calender#isLenient()
     */
    private static Date parseDateWithLeniency(String str, String[] parsePatterns, boolean lenient)
            throws ParseException {
        if (str == null || parsePatterns == null) {
            throw new IllegalArgumentException("Date and Patterns must not be null");
        }

        SimpleDateFormat parser = new SimpleDateFormat();
        parser.setLenient(lenient);
        ParsePosition pos = new ParsePosition(0);
        for (int i = 0; i < parsePatterns.length; i++) {

            String pattern = parsePatterns[i];

            // LANG-530 - need to make sure 'ZZ' output doesn't get passed to SimpleDateFormat
            if (parsePatterns[i].endsWith("ZZ")) {
                pattern = pattern.substring(0, pattern.length() - 1);
            }

            parser.applyPattern(pattern);
            pos.setIndex(0);

            String str2 = str;
            // LANG-530 - need to make sure 'ZZ' output doesn't hit SimpleDateFormat as it will ParseException
            if (parsePatterns[i].endsWith("ZZ")) {
                int signIdx = indexOfSignChars(str2, 0);
                while (signIdx >= 0) {
                    str2 = reformatTimezone(str2, signIdx);
                    signIdx = indexOfSignChars(str2, ++signIdx);
                }
            }

            Date date = parser.parse(str2, pos);
            if (date != null && pos.getIndex() == str2.length()) {
                return date;
            }
        }
        throw new ParseException("Unable to parse the date: " + str, -1);
    }

    /**
     * Index of sign charaters (i.e. '+' or '-').
     * 
     * @param str The string to search
     * @param startPos The start position
     * @return the index of the first sign character or -1 if not found
     */
    private static int indexOfSignChars(String str, int startPos) {
        int idx = StringUtils.indexOf(str, '+', startPos);
        if (idx < 0) {
            idx = StringUtils.indexOf(str, '-', startPos);
        }
        return idx;
    }

    /**
     * Reformat the timezone in a date string.
     * 
     * @param str The input string
     * @param signIdx The index position of the sign characters
     * @return The reformatted string
     */
    private static String reformatTimezone(String str, int signIdx) {
        String str2 = str;
        if (signIdx >= 0 && signIdx + 5 < str.length() && Character.isDigit(str.charAt(signIdx + 1))
                && Character.isDigit(str.charAt(signIdx + 2)) && str.charAt(signIdx + 3) == ':'
                && Character.isDigit(str.charAt(signIdx + 4)) && Character.isDigit(str.charAt(signIdx + 5))) {
            str2 = str.substring(0, signIdx + 3) + str.substring(signIdx + 4);
        }
        return str2;
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of years to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addYears(Date date, int amount) {
        return add(date, Calendar.YEAR, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of months to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addMonths(Date date, int amount) {
        return add(date, Calendar.MONTH, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of weeks to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addWeeks(Date date, int amount) {
        return add(date, Calendar.WEEK_OF_YEAR, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of days to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addDays(Date date, int amount) {
        return add(date, Calendar.DAY_OF_MONTH, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of hours to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addHours(Date date, int amount) {
        return add(date, Calendar.HOUR_OF_DAY, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of minutes to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addMinutes(Date date, int amount) {
        return add(date, Calendar.MINUTE, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of seconds to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addSeconds(Date date, int amount) {
        return add(date, Calendar.SECOND, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds a number of milliseconds to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     */
    public static Date addMilliseconds(Date date, int amount) {
        return add(date, Calendar.MILLISECOND, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Adds to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param calendarField the calendar field to add to
     * @param amount the amount to add, may be negative
     * @return the new date object with the amount added
     * @throws IllegalArgumentException if the date is null
     * @deprecated Will become privately scoped in 3.0
     */
    @Deprecated
    public static Date add(Date date, int calendarField, int amount) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        c.add(calendarField, amount);
        return c.getTime();
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the years field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setYears(Date date, int amount) {
        return set(date, Calendar.YEAR, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the months field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setMonths(Date date, int amount) {
        return set(date, Calendar.MONTH, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the day of month field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setDays(Date date, int amount) {
        return set(date, Calendar.DAY_OF_MONTH, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the hours field to a date returning a new object. Hours range from 0-23. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setHours(Date date, int amount) {
        return set(date, Calendar.HOUR_OF_DAY, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the minute field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setMinutes(Date date, int amount) {
        return set(date, Calendar.MINUTE, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the seconds field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setSeconds(Date date, int amount) {
        return set(date, Calendar.SECOND, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the miliseconds field to a date returning a new object. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    public static Date setMilliseconds(Date date, int amount) {
        return set(date, Calendar.MILLISECOND, amount);
    }

    // -----------------------------------------------------------------------
    /**
     * Sets the specified field to a date returning a new object. This does not use a lenient calendar. The original date object is unchanged.
     * 
     * @param date the date, not null
     * @param calendarField the calendar field to set the amount to
     * @param amount the amount to set
     * @return a new Date object set with the specified value
     * @throws IllegalArgumentException if the date is null
     * @since 2.4
     */
    private static Date set(Date date, int calendarField, int amount) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        // getInstance() returns a new object, so this method is thread safe.
        Calendar c = Calendar.getInstance();
        c.setLenient(false);
        c.setTime(date);
        c.set(calendarField, amount);
        return c.getTime();
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Round this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April
     * 2002 0:00:00.000.
     * </p>
     * <p>
     * For a date in a timezone that handles the change to daylight saving time, rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight saving time begins at 02:00 on March 30.
     * Rounding a date that crosses this time would produce the following values:
     * <ul>
     * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
     * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Date round(Date date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar gval = Calendar.getInstance();
        gval.setTime(date);
        modify(gval, field, MODIFY_ROUND);
        return gval.getTime();
    }

    /**
     * <p>
     * Round this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April
     * 2002 0:00:00.000.
     * </p>
     * <p>
     * For a date in a timezone that handles the change to daylight saving time, rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight saving time begins at 02:00 on March 30.
     * Rounding a date that crosses this time would produce the following values:
     * <ul>
     * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
     * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date (a different object)
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Calendar round(Calendar date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar rounded = (Calendar) date.clone();
        modify(rounded, field, MODIFY_ROUND);
        return rounded;
    }

    /**
     * <p>
     * Round this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if this was passed with HOUR, it would return 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it would return 1 April
     * 2002 0:00:00.000.
     * </p>
     * <p>
     * For a date in a timezone that handles the change to daylight saving time, rounding to Calendar.HOUR_OF_DAY will behave as follows. Suppose daylight saving time begins at 02:00 on March 30.
     * Rounding a date that crosses this time would produce the following values:
     * <ul>
     * <li>March 30, 2003 01:10 rounds to March 30, 2003 01:00</li>
     * <li>March 30, 2003 01:40 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:10 rounds to March 30, 2003 03:00</li>
     * <li>March 30, 2003 02:40 rounds to March 30, 2003 04:00</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, either Date or Calendar
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ClassCastException if the object type is not a <code>Date</code> or <code>Calendar</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Date round(Object date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (date instanceof Date) {
            return round((Date) date, field);
        } else if (date instanceof Calendar) {
            return round((Calendar) date, field).getTime();
        } else {
            throw new ClassCastException("Could not round " + date);
        }
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Truncate this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Date truncate(Date date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar gval = Calendar.getInstance();
        gval.setTime(date);
        modify(gval, field, MODIFY_TRUNCATE);
        return gval.getTime();
    }

    /**
     * <p>
     * Truncate this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date (a different object)
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Calendar truncate(Calendar date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar truncated = (Calendar) date.clone();
        modify(truncated, field, MODIFY_TRUNCATE);
        return truncated;
    }

    /**
     * <p>
     * Truncate this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with, either <code>Date</code> or <code>Calendar</code>
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ClassCastException if the object type is not a <code>Date</code> or <code>Calendar</code>
     * @throws ArithmeticException if the year is over 280 million
     */
    public static Date truncate(Object date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (date instanceof Date) {
            return truncate((Date) date, field);
        } else if (date instanceof Calendar) {
            return truncate((Calendar) date, field).getTime();
        } else {
            throw new ClassCastException("Could not truncate " + date);
        }
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Ceil this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     * @since 2.5
     */
    public static Date ceiling(Date date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar gval = Calendar.getInstance();
        gval.setTime(date);
        modify(gval, field, MODIFY_CEILING);
        return gval.getTime();
    }

    /**
     * <p>
     * Ceil this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date (a different object)
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ArithmeticException if the year is over 280 million
     * @since 2.5
     */
    public static Calendar ceiling(Calendar date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar ceiled = (Calendar) date.clone();
        modify(ceiled, field, MODIFY_CEILING);
        return ceiled;
    }

    /**
     * <p>
     * Ceil this date, leaving the field specified as the most significant field.
     * </p>
     * <p>
     * For example, if you had the datetime of 28 Mar 2002 13:45:01.231, if you passed with HOUR, it would return 28 Mar 2002 13:00:00.000. If this was passed with MONTH, it would return 1 Mar 2002
     * 0:00:00.000.
     * </p>
     * 
     * @param date the date to work with, either <code>Date</code> or <code>Calendar</code>
     * @param field the field from <code>Calendar</code> or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ClassCastException if the object type is not a <code>Date</code> or <code>Calendar</code>
     * @throws ArithmeticException if the year is over 280 million
     * @since 2.5
     */
    public static Date ceiling(Object date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (date instanceof Date) {
            return ceiling((Date) date, field);
        } else if (date instanceof Calendar) {
            return ceiling((Calendar) date, field).getTime();
        } else {
            throw new ClassCastException("Could not find ceiling of for type: " + date.getClass());
        }
    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * Internal calculation method.
     * </p>
     * 
     * @param val the calendar
     * @param field the field constant
     * @param modType type to truncate, round or ceiling
     * @throws ArithmeticException if the year is over 280 million
     */
    static void modify(Calendar val, int field, int modType) {
        if (val.get(Calendar.YEAR) > 280000000) {
            throw new ArithmeticException("Calendar value too large for accurate calculations");
        }

        if (field == Calendar.MILLISECOND) {
            return;
        }

        // ----------------- Fix for LANG-59 ---------------------- START ---------------
        // see http://issues.apache.org/jira/browse/LANG-59
        //
        // Manually truncate milliseconds, seconds and minutes, rather than using
        // Calendar methods.

        Date date = val.getTime();
        long time = date.getTime();
        boolean done = false;

        // truncate milliseconds
        int millisecs = val.get(Calendar.MILLISECOND);
        if (MODIFY_TRUNCATE == modType || millisecs < 500) {
            time = time - millisecs;
        }
        if (field == Calendar.SECOND) {
            done = true;
        }

        // truncate seconds
        int seconds = val.get(Calendar.SECOND);
        if (!done && (MODIFY_TRUNCATE == modType || seconds < 30)) {
            time = time - (seconds * 1000L);
        }
        if (field == Calendar.MINUTE) {
            done = true;
        }

        // truncate minutes
        int minutes = val.get(Calendar.MINUTE);
        if (!done && (MODIFY_TRUNCATE == modType || minutes < 30)) {
            time = time - (minutes * 60000L);
        }

        // reset time
        if (date.getTime() != time) {
            date.setTime(time);
            val.setTime(date);
        }
        // ----------------- Fix for LANG-59 ----------------------- END ----------------

        boolean roundUp = false;
        for (int i = 0; i < fields.length; i++) {
            for (int j = 0; j < fields[i].length; j++) {
                if (fields[i][j] == field) {
                    // This is our field... we stop looping
                    if (modType == MODIFY_CEILING || (modType == MODIFY_ROUND && roundUp)) {
                        if (field == DateUtils.SEMI_MONTH) {
                            // This is a special case that's hard to generalize
                            // If the date is 1, we round up to 16, otherwise
                            // we subtract 15 days and add 1 month
                            if (val.get(Calendar.DATE) == 1) {
                                val.add(Calendar.DATE, 15);
                            } else {
                                val.add(Calendar.DATE, -15);
                                val.add(Calendar.MONTH, 1);
                            }
                            // ----------------- Fix for LANG-440 ---------------------- START ---------------
                        } else if (field == Calendar.AM_PM) {
                            // This is a special case
                            // If the time is 0, we round up to 12, otherwise
                            // we subtract 12 hours and add 1 day
                            if (val.get(Calendar.HOUR_OF_DAY) == 0) {
                                val.add(Calendar.HOUR_OF_DAY, 12);
                            } else {
                                val.add(Calendar.HOUR_OF_DAY, -12);
                                val.add(Calendar.DATE, 1);
                            }
                            // ----------------- Fix for LANG-440 ---------------------- END ---------------
                        } else {
                            // We need at add one to this field since the
                            // last number causes us to round up
                            val.add(fields[i][0], 1);
                        }
                    }
                    return;
                }
            }
            // We have various fields that are not easy roundings
            int offset = 0;
            boolean offsetSet = false;
            // These are special types of fields that require different rounding rules
            switch (field) {
            case DateUtils.SEMI_MONTH:
                if (fields[i][0] == Calendar.DATE) {
                    // If we're going to drop the DATE field's value,
                    // we want to do this our own way.
                    // We need to subtrace 1 since the date has a minimum of 1
                    offset = val.get(Calendar.DATE) - 1;
                    // If we're above 15 days adjustment, that means we're in the
                    // bottom half of the month and should stay accordingly.
                    if (offset >= 15) {
                        offset -= 15;
                    }
                    // Record whether we're in the top or bottom half of that range
                    roundUp = offset > 7;
                    offsetSet = true;
                }
                break;
            case Calendar.AM_PM:
                if (fields[i][0] == Calendar.HOUR_OF_DAY) {
                    // If we're going to drop the HOUR field's value,
                    // we want to do this our own way.
                    offset = val.get(Calendar.HOUR_OF_DAY);
                    if (offset >= 12) {
                        offset -= 12;
                    }
                    roundUp = offset >= 6;
                    offsetSet = true;
                }
                break;
            }
            if (!offsetSet) {
                int min = val.getActualMinimum(fields[i][0]);
                int max = val.getActualMaximum(fields[i][0]);
                // Calculate the offset from the minimum allowed value
                offset = val.get(fields[i][0]) - min;
                // Set roundUp if this is more than half way between the minimum and maximum
                roundUp = offset > ((max - min) / 2);
            }
            // We need to remove this field
            if (offset != 0) {
                val.set(fields[i][0], val.get(fields[i][0]) - offset);
            }
        }
        throw new IllegalArgumentException("The field " + field + " is not supported");

    }

    // -----------------------------------------------------------------------
    /**
     * <p>
     * This constructs an <code>Iterator</code> over each day in a date range defined by a focus date and range style.
     * </p>
     * <p>
     * For instance, passing Thursday, July 4, 2002 and a <code>RANGE_MONTH_SUNDAY</code> will return an <code>Iterator</code> that starts with Sunday, June 30, 2002 and ends with Saturday, August 3,
     * 2002, returning a Calendar instance for each intermediate day.
     * </p>
     * <p>
     * This method provides an iterator that returns Calendar objects. The days are progressed using {@link Calendar#add(int, int)}.
     * </p>
     * 
     * @param focus the date to work with, not null
     * @param rangeStyle the style constant to use. Must be one of {@link DateUtils#RANGE_MONTH_SUNDAY}, {@link DateUtils#RANGE_MONTH_MONDAY}, {@link DateUtils#RANGE_WEEK_SUNDAY},
     *        {@link DateUtils#RANGE_WEEK_MONDAY}, {@link DateUtils#RANGE_WEEK_RELATIVE}, {@link DateUtils#RANGE_WEEK_CENTER}
     * @return the date iterator, which always returns Calendar instances
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws IllegalArgumentException if the rangeStyle is invalid
     */
    public static Iterator iterator(Date focus, int rangeStyle) {
        if (focus == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar gval = Calendar.getInstance();
        gval.setTime(focus);
        return iterator(gval, rangeStyle);
    }

    /**
     * <p>
     * This constructs an <code>Iterator</code> over each day in a date range defined by a focus date and range style.
     * </p>
     * <p>
     * For instance, passing Thursday, July 4, 2002 and a <code>RANGE_MONTH_SUNDAY</code> will return an <code>Iterator</code> that starts with Sunday, June 30, 2002 and ends with Saturday, August 3,
     * 2002, returning a Calendar instance for each intermediate day.
     * </p>
     * <p>
     * This method provides an iterator that returns Calendar objects. The days are progressed using {@link Calendar#add(int, int)}.
     * </p>
     * 
     * @param focus the date to work with
     * @param rangeStyle the style constant to use. Must be one of {@link DateUtils#RANGE_MONTH_SUNDAY}, {@link DateUtils#RANGE_MONTH_MONDAY}, {@link DateUtils#RANGE_WEEK_SUNDAY},
     *        {@link DateUtils#RANGE_WEEK_MONDAY}, {@link DateUtils#RANGE_WEEK_RELATIVE}, {@link DateUtils#RANGE_WEEK_CENTER}
     * @return the date iterator
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws IllegalArgumentException if the rangeStyle is invalid
     */
    public static Iterator iterator(Calendar focus, int rangeStyle) {
        if (focus == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar start = null;
        Calendar end = null;
        int startCutoff = Calendar.SUNDAY;
        int endCutoff = Calendar.SATURDAY;
        switch (rangeStyle) {
        case RANGE_MONTH_SUNDAY:
        case RANGE_MONTH_MONDAY:
            // Set start to the first of the month
            start = truncate(focus, Calendar.MONTH);
            // Set end to the last of the month
            end = (Calendar) start.clone();
            end.add(Calendar.MONTH, 1);
            end.add(Calendar.DATE, -1);
            // Loop start back to the previous sunday or monday
            if (rangeStyle == RANGE_MONTH_MONDAY) {
                startCutoff = Calendar.MONDAY;
                endCutoff = Calendar.SUNDAY;
            }
            break;
        case RANGE_WEEK_SUNDAY:
        case RANGE_WEEK_MONDAY:
        case RANGE_WEEK_RELATIVE:
        case RANGE_WEEK_CENTER:
            // Set start and end to the current date
            start = truncate(focus, Calendar.DATE);
            end = truncate(focus, Calendar.DATE);
            switch (rangeStyle) {
            case RANGE_WEEK_SUNDAY:
                // already set by default
                break;
            case RANGE_WEEK_MONDAY:
                startCutoff = Calendar.MONDAY;
                endCutoff = Calendar.SUNDAY;
                break;
            case RANGE_WEEK_RELATIVE:
                startCutoff = focus.get(Calendar.DAY_OF_WEEK);
                endCutoff = startCutoff - 1;
                break;
            case RANGE_WEEK_CENTER:
                startCutoff = focus.get(Calendar.DAY_OF_WEEK) - 3;
                endCutoff = focus.get(Calendar.DAY_OF_WEEK) + 3;
                break;
            }
            break;
        default:
            throw new IllegalArgumentException("The range style " + rangeStyle + " is not valid.");
        }
        if (startCutoff < Calendar.SUNDAY) {
            startCutoff += 7;
        }
        if (startCutoff > Calendar.SATURDAY) {
            startCutoff -= 7;
        }
        if (endCutoff < Calendar.SUNDAY) {
            endCutoff += 7;
        }
        if (endCutoff > Calendar.SATURDAY) {
            endCutoff -= 7;
        }
        while (start.get(Calendar.DAY_OF_WEEK) != startCutoff) {
            start.add(Calendar.DATE, -1);
        }
        while (end.get(Calendar.DAY_OF_WEEK) != endCutoff) {
            end.add(Calendar.DATE, 1);
        }
        return new DateIterator(start, end);
    }

    /**
     * <p>
     * This constructs an <code>Iterator</code> over each day in a date range defined by a focus date and range style.
     * </p>
     * <p>
     * For instance, passing Thursday, July 4, 2002 and a <code>RANGE_MONTH_SUNDAY</code> will return an <code>Iterator</code> that starts with Sunday, June 30, 2002 and ends with Saturday, August 3,
     * 2002, returning a Calendar instance for each intermediate day.
     * </p>
     * 
     * @param focus the date to work with, either <code>Date</code> or <code>Calendar</code>
     * @param rangeStyle the style constant to use. Must be one of the range styles listed for the {@link #iterator(Calendar, int)} method.
     * @return the date iterator
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ClassCastException if the object type is not a <code>Date</code> or <code>Calendar</code>
     */
    public static Iterator iterator(Object focus, int rangeStyle) {
        if (focus == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (focus instanceof Date) {
            return iterator((Date) focus, rangeStyle);
        } else if (focus instanceof Calendar) {
            return iterator((Calendar) focus, rangeStyle);
        } else {
            throw new ClassCastException("Could not iterate based on " + focus);
        }
    }

    /**
     * <p>
     * Returns the number of milliseconds within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the milliseconds of any date will only return the number of milliseconds of the current second (resulting in a number between 0 and 999). This method will retrieve the number of
     * milliseconds for any fragment. For example, if you want to calculate the number of milliseconds past today, your fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all
     * milliseconds of the past hour(s), minutes(s) and second(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a SECOND field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10538 (10*1000 + 538)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in milliseconds)</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @return number of milliseconds within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInMilliseconds(Date date, int fragment) {
        return getFragment(date, fragment, Calendar.MILLISECOND);
    }

    /**
     * <p>
     * Returns the number of seconds within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the seconds of any date will only return the number of seconds of the current minute (resulting in a number between 0 and 59). This method will retrieve the number of seconds for any
     * fragment. For example, if you want to calculate the number of seconds past today, your fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all seconds of the past hour(s) and
     * minutes(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a SECOND field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10 (equivalent to deprecated date.getSeconds())</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10 (equivalent to deprecated date.getSeconds())</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 26110 (7*3600 + 15*60 + 10)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in seconds)</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @return number of seconds within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInSeconds(Date date, int fragment) {
        return getFragment(date, fragment, Calendar.SECOND);
    }

    /**
     * <p>
     * Returns the number of minutes within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the minutes of any date will only return the number of minutes of the current hour (resulting in a number between 0 and 59). This method will retrieve the number of minutes for any
     * fragment. For example, if you want to calculate the number of minutes past this month, your fragment is Calendar.MONTH. The result will be all minutes of the past day(s) and hour(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a MINUTE field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will return 15 (equivalent to deprecated date.getMinutes())</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will return 15 (equivalent to deprecated date.getMinutes())</li>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 15</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 435 (7*60 + 15)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in minutes)</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @return number of minutes within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInMinutes(Date date, int fragment) {
        return getFragment(date, fragment, Calendar.MINUTE);
    }

    /**
     * <p>
     * Returns the number of hours within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the hours of any date will only return the number of hours of the current day (resulting in a number between 0 and 23). This method will retrieve the number of hours for any fragment.
     * For example, if you want to calculate the number of hours past this month, your fragment is Calendar.MONTH. The result will be all hours of the past day(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a HOUR field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7 (equivalent to deprecated date.getHours())</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7 (equivalent to deprecated date.getHours())</li>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 7</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 127 (5*24 + 7)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in hours)</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @return number of hours within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInHours(Date date, int fragment) {
        return getFragment(date, fragment, Calendar.HOUR_OF_DAY);
    }

    /**
     * <p>
     * Returns the number of days within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the days of any date will only return the number of days of the current month (resulting in a number between 1 and 31). This method will retrieve the number of days for any fragment. For
     * example, if you want to calculate the number of days past this year, your fragment is Calendar.YEAR. The result will be all days of the past month(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a DAY field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 28, 2008 with Calendar.MONTH as fragment will return 28 (equivalent to deprecated date.getDay())</li>
     * <li>February 28, 2008 with Calendar.MONTH as fragment will return 28 (equivalent to deprecated date.getDay())</li>
     * <li>January 28, 2008 with Calendar.YEAR as fragment will return 28</li>
     * <li>February 28, 2008 with Calendar.YEAR as fragment will return 59</li>
     * <li>January 28, 2008 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in days)</li>
     * </ul>
     * </p>
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @return number of days within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInDays(Date date, int fragment) {
        return getFragment(date, fragment, Calendar.DAY_OF_YEAR);
    }

    /**
     * <p>
     * Returns the number of milliseconds within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the milliseconds of any date will only return the number of milliseconds of the current second (resulting in a number between 0 and 999). This method will retrieve the number of
     * milliseconds for any fragment. For example, if you want to calculate the number of seconds past today, your fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all seconds of
     * the past hour(s), minutes(s) and second(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a MILLISECOND field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538 (equivalent to calendar.get(Calendar.MILLISECOND))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.SECOND as fragment will return 538 (equivalent to calendar.get(Calendar.MILLISECOND))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10538 (10*1000 + 538)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in milliseconds)</li>
     * </ul>
     * </p>
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @return number of milliseconds within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInMilliseconds(Calendar calendar, int fragment) {
        return getFragment(calendar, fragment, Calendar.MILLISECOND);
    }

    /**
     * <p>
     * Returns the number of seconds within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the seconds of any date will only return the number of seconds of the current minute (resulting in a number between 0 and 59). This method will retrieve the number of seconds for any
     * fragment. For example, if you want to calculate the number of seconds past today, your fragment is Calendar.DATE or Calendar.DAY_OF_YEAR. The result will be all seconds of the past hour(s) and
     * minutes(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a SECOND field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10 (equivalent to calendar.get(Calendar.SECOND))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MINUTE as fragment will return 10 (equivalent to calendar.get(Calendar.SECOND))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 26110 (7*3600 + 15*60 + 10)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in seconds)</li>
     * </ul>
     * </p>
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @return number of seconds within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInSeconds(Calendar calendar, int fragment) {
        return getFragment(calendar, fragment, Calendar.SECOND);
    }

    /**
     * <p>
     * Returns the number of minutes within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the minutes of any date will only return the number of minutes of the current hour (resulting in a number between 0 and 59). This method will retrieve the number of minutes for any
     * fragment. For example, if you want to calculate the number of minutes past this month, your fragment is Calendar.MONTH. The result will be all minutes of the past day(s) and hour(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a MINUTE field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will return 15 (equivalent to calendar.get(Calendar.MINUTES))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.HOUR_OF_DAY as fragment will return 15 (equivalent to calendar.get(Calendar.MINUTES))</li>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 15</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 435 (7*60 + 15)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in minutes)</li>
     * </ul>
     * </p>
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @return number of minutes within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInMinutes(Calendar calendar, int fragment) {
        return getFragment(calendar, fragment, Calendar.MINUTE);
    }

    /**
     * <p>
     * Returns the number of hours within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the hours of any date will only return the number of hours of the current day (resulting in a number between 0 and 23). This method will retrieve the number of hours for any fragment.
     * For example, if you want to calculate the number of hours past this month, your fragment is Calendar.MONTH. The result will be all hours of the past day(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a HOUR field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 1, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7 (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.DAY_OF_YEAR as fragment will return 7 (equivalent to calendar.get(Calendar.HOUR_OF_DAY))</li>
     * <li>January 1, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 7</li>
     * <li>January 6, 2008 7:15:10.538 with Calendar.MONTH as fragment will return 127 (5*24 + 7)</li>
     * <li>January 16, 2008 7:15:10.538 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in hours)</li>
     * </ul>
     * </p>
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @return number of hours within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInHours(Calendar calendar, int fragment) {
        return getFragment(calendar, fragment, Calendar.HOUR_OF_DAY);
    }

    /**
     * <p>
     * Returns the number of days within the fragment. All datefields greater than the fragment will be ignored.
     * </p>
     * <p>
     * Asking the days of any date will only return the number of days of the current month (resulting in a number between 1 and 31). This method will retrieve the number of days for any fragment. For
     * example, if you want to calculate the number of days past this year, your fragment is Calendar.YEAR. The result will be all days of the past month(s).
     * </p>
     * <p>
     * Valid fragments are: Calendar.YEAR, Calendar.MONTH, both Calendar.DAY_OF_YEAR and Calendar.DATE, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND and Calendar.MILLISECOND A fragment less
     * than or equal to a DAY field will return 0.
     * </p>
     * <p>
     * <ul>
     * <li>January 28, 2008 with Calendar.MONTH as fragment will return 28 (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li>
     * <li>February 28, 2008 with Calendar.MONTH as fragment will return 28 (equivalent to calendar.get(Calendar.DAY_OF_MONTH))</li>
     * <li>January 28, 2008 with Calendar.YEAR as fragment will return 28 (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li>
     * <li>February 28, 2008 with Calendar.YEAR as fragment will return 59 (equivalent to calendar.get(Calendar.DAY_OF_YEAR))</li>
     * <li>January 28, 2008 with Calendar.MILLISECOND as fragment will return 0 (a millisecond cannot be split in days)</li>
     * </ul>
     * </p>
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @return number of days within the fragment of date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    public static long getFragmentInDays(Calendar calendar, int fragment) {
        return getFragment(calendar, fragment, Calendar.DAY_OF_YEAR);
    }

    /**
     * Date-version for fragment-calculation in any unit
     * 
     * @param date the date to work with, not null
     * @param fragment the Calendar field part of date to calculate
     * @param unit Calendar field defining the unit
     * @return number of units within the fragment of the date
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    private static long getFragment(Date date, int fragment, int unit) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        return getFragment(calendar, fragment, unit);
    }

    /**
     * Calendar-version for fragment-calculation in any unit
     * 
     * @param calendar the calendar to work with, not null
     * @param fragment the Calendar field part of calendar to calculate
     * @param unit Calendar field defining the unit
     * @return number of units within the fragment of the calendar
     * @throws IllegalArgumentException if the date is <code>null</code> or fragment is not supported
     * @since 2.4
     */
    private static long getFragment(Calendar calendar, int fragment, int unit) {
        if (calendar == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        long millisPerUnit = getMillisPerUnit(unit);
        long result = 0;

        // Fragments bigger than a day require a breakdown to days
        switch (fragment) {
        case Calendar.YEAR:
            result += (calendar.get(Calendar.DAY_OF_YEAR) * MILLIS_PER_DAY) / millisPerUnit;
            break;
        case Calendar.MONTH:
            result += (calendar.get(Calendar.DAY_OF_MONTH) * MILLIS_PER_DAY) / millisPerUnit;
            break;
        }

        switch (fragment) {
        // Number of days already calculated for these cases
        case Calendar.YEAR:
        case Calendar.MONTH:

            // The rest of the valid cases
        case Calendar.DAY_OF_YEAR:
        case Calendar.DATE:
            result += (calendar.get(Calendar.HOUR_OF_DAY) * MILLIS_PER_HOUR) / millisPerUnit;
            //$FALL-THROUGH$
        case Calendar.HOUR_OF_DAY:
            result += (calendar.get(Calendar.MINUTE) * MILLIS_PER_MINUTE) / millisPerUnit;
            //$FALL-THROUGH$
        case Calendar.MINUTE:
            result += (calendar.get(Calendar.SECOND) * MILLIS_PER_SECOND) / millisPerUnit;
            //$FALL-THROUGH$
        case Calendar.SECOND:
            result += (calendar.get(Calendar.MILLISECOND) * 1) / millisPerUnit;
            break;
        case Calendar.MILLISECOND:
            break;// never useful
        default:
            throw new IllegalArgumentException("The fragment " + fragment + " is not supported");
        }
        return result;
    }

    /**
     * Returns the number of millis of a datefield, if this is a constant value
     * 
     * @param unit A Calendar field which is a valid unit for a fragment
     * @return number of millis
     * @throws IllegalArgumentException if date can't be represented in millisenconds
     * @since 2.4
     */
    private static long getMillisPerUnit(int unit) {
        long result = Long.MAX_VALUE;
        switch (unit) {
        case Calendar.DAY_OF_YEAR:
        case Calendar.DATE:
            result = MILLIS_PER_DAY;
            break;
        case Calendar.HOUR_OF_DAY:
            result = MILLIS_PER_HOUR;
            break;
        case Calendar.MINUTE:
            result = MILLIS_PER_MINUTE;
            break;
        case Calendar.SECOND:
            result = MILLIS_PER_SECOND;
            break;
        case Calendar.MILLISECOND:
            result = 1;
            break;
        default:
            throw new IllegalArgumentException("The unit " + unit + " cannot be represented is milleseconds");
        }
        return result;
    }

    /**
     * <p>
     * Date iterator.
     * </p>
     */
    static class DateIterator implements Iterator {

        private final Calendar endFinal;
        private final Calendar spot;

        /**
         * Constructs a DateIterator that ranges from one date to another.
         * 
         * @param startFinal start date (inclusive)
         * @param endFinal end date (not inclusive)
         */
        DateIterator(Calendar startFinal, Calendar endFinal) {
            super();
            this.endFinal = endFinal;
            spot = startFinal;
            spot.add(Calendar.DATE, -1);
        }

        /**
         * Has the iterator not reached the end date yet?
         * 
         * @return <code>true</code> if the iterator has yet to reach the end date
         */
        @Override
        public boolean hasNext() {
            return spot.before(endFinal);
        }

        /**
         * Return the next calendar in the iteration
         * 
         * @return Object calendar for the next date
         */
        @Override
        public Object next() {
            if (spot.equals(endFinal)) {
                throw new NoSuchElementException();
            }
            spot.add(Calendar.DATE, 1);
            return spot.clone();
        }

        /**
         * Always throws UnsupportedOperationException.
         * 
         * @throws UnsupportedOperationException
         * @see java.util.Iterator#remove()
         */
        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    // -------------------------------------------------------------------------
    // Deprecated int constants
    // TODO: Remove in 3.0

    /**
     * Number of milliseconds in a standard second.
     * 
     * @deprecated Use MILLIS_PER_SECOND. This will be removed in Commons Lang 3.0.
     */
    @Deprecated
    public static final int MILLIS_IN_SECOND = 1000;
    /**
     * Number of milliseconds in a standard minute.
     * 
     * @deprecated Use MILLIS_PER_MINUTE. This will be removed in Commons Lang 3.0.
     */
    @Deprecated
    public static final int MILLIS_IN_MINUTE = 60 * 1000;
    /**
     * Number of milliseconds in a standard hour.
     * 
     * @deprecated Use MILLIS_PER_HOUR. This will be removed in Commons Lang 3.0.
     */
    @Deprecated
    public static final int MILLIS_IN_HOUR = 60 * 60 * 1000;
    /**
     * Number of milliseconds in a standard day.
     * 
     * @deprecated Use MILLIS_PER_DAY. This will be removed in Commons Lang 3.0.
     */
    @Deprecated
    public static final int MILLIS_IN_DAY = 24 * 60 * 60 * 1000;

}