Java Utililty Methods Day

Calendar calendar = Calendar.getInstance(Locale.CHINA);
calendar.setTime(toDate(date));
calendar.set(Calendar.DATE, calendar.get(Calendar.DATE) + offset);
SimpleDateFormat sdf = new SimpleDateFormat(format);
return sdf.format(calendar.getTime());

String day = null;
DateFormat f = new SimpleDateFormat("EEE");
try {
    day = f.format(d1);
} catch (Exception e) {
    e.printStackTrace();
return day;
...

String dia = null;
Calendar calendar = Calendar.getInstance();
calendar.setTime(convertStringToDate(strDate));
switch (calendar.get(Calendar.DAY_OF_WEEK)) {
case Calendar.SUNDAY:
    dia = "DOMINGO";
    break;
case Calendar.MONDAY:
...

GregorianCalendar rightNow = new GregorianCalendar(Integer.parseInt(bday.substring(0, 4)),
        Integer.parseInt(bday.substring(4, 6)) - 1, Integer.parseInt(bday.substring(6, 8)));
int i = 0;
String s = null;
ArrayList al = new ArrayList();
al.add(bday);
while (true) {
    i++;
...

List<String> returnValue = new ArrayList<String>();
SimpleDateFormat sdf = new SimpleDateFormat(format);
Calendar c = Calendar.getInstance();
c.setTime(day);
for (int i = 0; i < preDays; i++) {
    c.add(Calendar.DAY_OF_YEAR, -1);
    returnValue.add(new String(sdf.format(c.getTime())));
return returnValue;

return (int) ((ed.getTime() - sd.getTime()) / (3600 * 24 * 1000));

StringBuilder sb = new StringBuilder();
long starttime = stringToTime("yyyyMMdd", yyyy + "0101").getTime();
long lasttime = stringToTime("yyyyMMdd", yyyy + "1231").getTime();
for (; starttime <= lasttime; starttime += 1000 * 3600 * 24) {
    sb.append(timeToString("yyyyMMdd", new Date(starttime)));
    sb.append(':');
return sb.toString().split(":");
...

Date date = new Date();
long time = date.getTime() / 1000L - (interval * 60 * 60 * 24);
date.setTime(time * 1000L);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
try {
    return format.format(date);
} catch (Exception ex) {
    System.out.println(ex.getMessage());
...

List<String> list = new ArrayList<String>();
int maxDate = getMaxDayByYearMonth(ym);
for (int i = 1; i <= maxDate; i++) {
    String d = String.valueOf(i < 10 ? "0" + i : i);
    list.add(ym + "-" + d);
return list;

Date curDate = strToDate(date);
Calendar calendar = Calendar.getInstance();
calendar.setTime(curDate);
return calendar.getActualMaximum(Calendar.DAY_OF_MONTH);