Here you can find the source of incrementMonth(long date, int increment)
private static long incrementMonth(long date, int increment)
//package com.java2s; /*//w ww . j a v a 2 s. c o m * $Id: DateUtils.java,v 1.1 2004/08/12 00:24:33 dmouse Exp $ * * Copyright 2004 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ import java.util.*; public class Main { private static Calendar CALENDAR = Calendar.getInstance(); private static long incrementMonth(long date, int increment) { Calendar calendar = CALENDAR; synchronized (calendar) { calendar.setTimeInMillis(date); calendar.add(Calendar.MONTH, increment); return calendar.getTimeInMillis(); } } }