时间对比

1:calender 常量

Calendar cal = Calendar.getInstance();    

//当前年     
int year = cal.get(Calendar.YEAR);    
    
//当前月 Calendar.MONTH从0开始     
int month = (cal.get(Calendar.MONTH))+1;    
    
//当前月的第几天:即当前日     
int day_of_month = cal.get(Calendar.DAY_OF_MONTH);    
//Calendar.DAY_OF_MONTH 和 Calendar.DATE 是等价的     
int date = cal.get(Calendar.DATE);    

//当前时钟:HOUR_OF_DAY-24小时制     
int hour24 = cal.get(Calendar.HOUR_OF_DAY);    
//HOUR-12小时制     
int hour12 = cal.get(Calendar.HOUR);    

//当前:分钟     
int minute = cal.get(Calendar.MINUTE);    

//当前秒     
int second = cal.get(Calendar.SECOND);    

// 星期几 Calendar.DAY_OF_WEEK用数字（1~7）表示（星期日~星期六）     
int day_of_week = cal.get(Calendar.DAY_OF_WEEK)-1;     
    
//0-上午；1-下午     
int ampm = cal.get(Calendar.AM_PM);    
    
//当前年的第几周     
int week_of_year = cal.get(Calendar.WEEK_OF_YEAR);    
     
//当前月的星期数     
int week_of_month = cal.get(Calendar.WEEK_OF_MONTH);    
    
//当前月中的第几个星期     
int day_of_week_in_month = cal.get(Calendar.DAY_OF_WEEK_IN_MONTH);    

//当前年的第几天     
int day_of_year = cal.get(Calendar.DAY_OF_YEAR);

 2：工具类

 package com.dayatang.utils;

import java.security.InvalidParameterException;
import java.text.ParseException;
import java.util.Calendar;
import java.util.Date;

public class DateUtils {

	private static final long MILLIS_IN_A_SECOND = 1000;

	private static final long SECONDS_IN_A_MINUTE = 60;

	private static final long MINUTES_IN_AN_HOUR = 60;

	private static final long HOURS_IN_A_DAY = 24;

	private static final int DAYS_IN_A_WEEK = 7;

	private static final int MONTHS_IN_A_YEAR = 12;

	//private static final int[] daysInMonth = new int[] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

	/**
	 * 最小日期，设定为1000年1月1日
	 */
	public static final Date MIN_DATE = date(1000, 1, 1);

	/**
	 * 最大日期，设定为8888年1月1日
	 */
	public static final Date MAX_DATE = date(8888, 1, 1);
	

	/**
	 * 根据年月日构建日期对象。注意月份是从1开始计数的，即month为1代表1月份。
	 * @param year 年
	 * @param month 月。注意1代表1月份，依此类推。
	 * @param day 日
	 * @return
	 */
	public static Date date(int year, int month, int date) {
		Calendar calendar = Calendar.getInstance();
		calendar.set(year, month - 1, date, 0, 0, 0);
		calendar.set(Calendar.MILLISECOND, 0);
		return calendar.getTime();
	}
	
	/**
	 * 计算两个日期（不包括时间）之间相差的周年数
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static int getYearDiff(Date date1, Date date2) {
		if (date1 == null || date2 == null) {
			throw new InvalidParameterException(
					"date1 and date2 cannot be null!");
		}
		if (date1.after(date2)) {
			throw new InvalidParameterException("date1 cannot be after date2!");
		}

		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date1);
		int year1 = calendar.get(Calendar.YEAR);
		int month1 = calendar.get(Calendar.MONTH);
		int day1 = calendar.get(Calendar.DATE);

		calendar.setTime(date2);
		int year2 = calendar.get(Calendar.YEAR);
		int month2 = calendar.get(Calendar.MONTH);
		int day2 = calendar.get(Calendar.DATE);

		int result = year2 - year1;
		if (month2 < month1) {
			result--;
		} else if (month2 == month1 && day2 < day1) {
			result--;
		}
		return result;
	}

	/**
	 * 计算两个日期（不包括时间）之间相差的整月数
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static int getMonthDiff(Date date1, Date date2) {
		if (date1 == null || date2 == null) {
			throw new InvalidParameterException(
					"date1 and date2 cannot be null!");
		}
		if (date1.after(date2)) {
			throw new InvalidParameterException("date1 cannot be after date2!");
		}

		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date1);
		int year1 = calendar.get(Calendar.YEAR);
		int month1 = calendar.get(Calendar.MONTH);
		int day1 = calendar.get(Calendar.DATE);

		calendar.setTime(date2);
		int year2 = calendar.get(Calendar.YEAR);
		int month2 = calendar.get(Calendar.MONTH);
		int day2 = calendar.get(Calendar.DATE);

		int months = 0;
		if (day2 >= day1) {
			months = month2 - month1;
		} else {
			months = month2 - month1 - 1;
		}
		return (year2 - year1) * MONTHS_IN_A_YEAR + months;
	}

	/**
	 * 统计两个日期之间包含的天数。包含date1，但不包含date2
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static int getDayDiff(Date date1, Date date2) {
		if (date1 == null || date2 == null) {
			throw new InvalidParameterException(
					"date1 and date2 cannot be null!");
		}
		Date startDate = org.apache.commons.lang3.time.DateUtils.truncate(
				date1, Calendar.DATE);
		Date endDate = org.apache.commons.lang3.time.DateUtils.truncate(date2,
				Calendar.DATE);
		if (startDate.after(endDate)) {
			throw new InvalidParameterException("date1 cannot be after date2!");
		}
		long millSecondsInOneDay = HOURS_IN_A_DAY * MINUTES_IN_AN_HOUR
				* SECONDS_IN_A_MINUTE * MILLIS_IN_A_SECOND;
		return (int) ((endDate.getTime() - startDate.getTime()) / millSecondsInOneDay);
	}

	/**
	 * 计算time2比time1晚多少分钟，忽略日期部分
	 * 
	 * @param time1
	 * @param time2
	 * @return
	 */
	public static int getMinuteDiffByTime(Date time1, Date time2) {
		long startMil = 0;
		long endMil = 0;
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(time1);
		calendar.set(1900, 1, 1);
		startMil = calendar.getTimeInMillis();
		calendar.setTime(time2);
		calendar.set(1900, 1, 1);
		endMil = calendar.getTimeInMillis();
		return (int) ((endMil - startMil) / MILLIS_IN_A_SECOND / SECONDS_IN_A_MINUTE);
	}

	/**
	 * 计算指定日期的前一天
	 * 
	 * @param date
	 * @return
	 */
	public static Date getPrevDay(Date date) {
		return org.apache.commons.lang3.time.DateUtils.addDays(date, -1);
	}

	/**
	 * 计算指定日期的后一天
	 * 
	 * @param date
	 * @return
	 */
	public static Date getNextDay(Date date) {
		return org.apache.commons.lang3.time.DateUtils.addDays(date, 1);
	}

	/**
	 * 判断date1是否在date2之后，忽略时间部分
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static boolean isDateAfter(Date date1, Date date2) {
		Date theDate1 = org.apache.commons.lang3.time.DateUtils.truncate(date1,
				Calendar.DATE);
		Date theDate2 = org.apache.commons.lang3.time.DateUtils.truncate(date2,
				Calendar.DATE);
		return theDate1.after(theDate2);
	}

	/**
	 * 判断date1是否在date2之前，忽略时间部分
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static boolean isDateBefore(Date date1, Date date2) {
		return isDateAfter(date2, date1);
	}

	/**
	 * 判断time1是否在time2之后，忽略日期部分
	 * 
	 * @param time1
	 * @param time2
	 * @return
	 */
	public static boolean isTimeAfter(Date time1, Date time2) {
		Calendar calendar1 = Calendar.getInstance();
		calendar1.setTime(time1);
		calendar1.set(1900, 1, 1);
		Calendar calendar2 = Calendar.getInstance();
		calendar2.setTime(time2);
		calendar2.set(1900, 1, 1);
		return calendar1.after(calendar2);
	}

	/**
	 * 判断time1是否在time2之前，忽略日期部分
	 * 
	 * @param time1
	 * @param time2
	 * @return
	 */
	public static boolean isTimeBefore(Date time1, Date time2) {
		return isTimeAfter(time2, time1);
	}

	/**
	 * 判断两个日期是否同一天（忽略时间部分）
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static boolean isSameDay(Date date1, Date date2) {
		return org.apache.commons.lang3.time.DateUtils.isSameDay(date1, date2);
	}

	/**
	 * 判断两个日历天是否同一天（忽略时间部分）
	 * 
	 * @param date1
	 * @param date2
	 * @return
	 */
	public static boolean isSameDay(Calendar date1, Calendar date2) {
		return org.apache.commons.lang3.time.DateUtils.isSameDay(date1, date2);
	}

	/**
	 * 将字符串形式的日期表示解析为日期对象
	 * 
	 * @param dateString
	 * @return
	 */
	public static Date parseDate(String dateString) {
		try {
			return org.apache.commons.lang3.time.DateUtils.parseDate(
					dateString, new String[] { "yyyy-MM-dd", "yyyy-M-d",
							"yyyy-MM-d", "yyyy-M-dd" });
		} catch (ParseException e) {
			return null;
		}
	}

	/**
	 * 将字符串形式的时间表示解析为日期时间对象
	 * 
	 * @param timeString
	 * @return
	 */
	public static Date parseTime(String timeString) {
		try {
			return org.apache.commons.lang3.time.DateUtils.parseDate(
					timeString, new String[] { "hh:mm:ss", "h:m:s", "hh:mm",
							"h:m" });
		} catch (ParseException e) {
			return null;
		}
	}

	/**
	 * 将字符串形式的日期时间表示解析为时间对象
	 * 
	 * @param timeString
	 * @return
	 */
	public static Date parseDateTime(String timeString) {
		try {
			return org.apache.commons.lang3.time.DateUtils.parseDate(
					timeString, new String[] { "yyyy-MM-dd HH:mm:ss",
							"yyyy-M-d H:m:s", "yyyy-MM-dd H:m:s",
							"yyyy-M-d HH:mm:ss" });
		} catch (ParseException e) {
			return null;
		}
	}

	/**
	 * 计算两个日期之间包含的星期X的天数。
	 * 
	 * @param fromDate
	 *            起始日期
	 * @param toDate
	 *            结束日期
	 * @param dayOfWeek
	 *            星期，例如星期三，星期四
	 * @return
	 */
	public static int getWeekDaysBetween(Date fromDate, Date toDate,
			int dayOfWeek) {
		int result = 0;
		Date firstDate = getFirstWeekdayBetween(fromDate, toDate, dayOfWeek);
		if (firstDate == null) {
			return 0;
		}
		Calendar aDay = Calendar.getInstance();
		aDay.setTime(firstDate);
		while (aDay.getTime().before(toDate)) {
			result++;
			aDay.add(Calendar.DATE, DAYS_IN_A_WEEK);
		}
		return result;
	}

	/**
	 * 获取在两个日期之间的第一个星期X
	 * 
	 * @param fromDate
	 *            起始日期
	 * @param toDate
	 *            结束日期
	 * @param dayOfWeek
	 *            星期，例如星期三，星期四
	 * @return
	 */
	public static Date getFirstWeekdayBetween(Date fromDate, Date toDate,
			int dayOfWeek) {
		Calendar aDay = Calendar.getInstance();
		aDay.setTime(fromDate);
		while (aDay.getTime().before(toDate)) {
			if (aDay.get(Calendar.DAY_OF_WEEK) == dayOfWeek) {
				return aDay.getTime();
			}
			aDay.add(Calendar.DATE, 1);
		}
		return null;
	}

	/**
	 * 取得参数year指定的年份的总天数
	 * 
	 * @param year
	 * @return
	 */
	public static int getDaysInYear(int year) {
		Calendar aDay = Calendar.getInstance();
		aDay.set(year, 1, 1);
		Date from = aDay.getTime();
		aDay.set(year + 1, 1, 1);
		Date to = aDay.getTime();
		return getDayDiff(from, to);
	}

	/**
	 * 取得指定年月的总天数
	 * 
	 * @param year
	 * @param month
	 * @return
	 */
	public static int getDaysInMonth(int year, int month) {
		Calendar aDay = Calendar.getInstance();
		aDay.set(year, month, 1);
		Date from = aDay.getTime();
		if (month == Calendar.DECEMBER) {
			aDay.set(year + 1, Calendar.JANUARY, 1);
		} else {
			aDay.set(year, month + 1, 1);
		}
		Date to = aDay.getTime();
		return getDayDiff(from, to);
	}

	/**
	 * 获得指定日期的年份
	 * 
	 * @param date
	 * @return
	 */
	public static int getYear(Date date) {
		return getFieldValue(date, Calendar.YEAR);
	}

	/**
	 * 获得指定日期的月份
	 * 
	 * @param date
	 * @return
	 */
	public static int getMonth(Date date) {
		return getFieldValue(date, Calendar.MONTH) + 1;
	}

	/**
	 * 获得指定日期是当年的第几天
	 * 
	 * @param date
	 * @return
	 */
	public static int getDayOfYear(Date date) {
		return getFieldValue(date, Calendar.DAY_OF_YEAR);
	}

	/**
	 * 获得指定日期是当月的第几天
	 * 
	 * @param date
	 * @return
	 */
	public static int getDayOfMonth(Date date) {
		return getFieldValue(date, Calendar.DAY_OF_MONTH);
	}

	/**
	 * 获得指定日期是当周的第几天
	 * 
	 * @param date
	 * @return
	 */
	public static int getDayOfWeek(Date date) {
		return getFieldValue(date, Calendar.DAY_OF_WEEK);
	}

	private static int getFieldValue(Date date, int field) {
		if (date == null) {
			throw new InvalidParameterException("date cannot be null!");
		}
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(date);
		return calendar.get(field);
	}

	/**
	 * 获得指定日期之后一段时期的日期。例如某日期之后3天的日期等。
	 * @param origDate 基准日期
	 * @param amount 时间数量
	 * @param timeUnit 时间单位，如年、月、日等。用Calendar中的常量代表
	 * @return
	 */
	public static final Date dateAfter(Date origDate, int amount, int timeUnit) {
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(origDate);
		calendar.add(timeUnit, amount);
		return calendar.getTime();
	}

	/**
	 * 获得指定日期之前一段时期的日期。例如某日期之前3天的日期等。
	 * @param origDate 基准日期
	 * @param amount 时间数量
	 * @param timeUnit 时间单位，如年、月、日等。用Calendar中的常量代表
	 * @return
	 */
	public static final Date dateBefore(Date origDate, int amount, int timeUnit) {
		Calendar calendar = Calendar.getInstance();
		calendar.setTime(origDate);
		calendar.add(timeUnit, -amount);
		return calendar.getTime();
	}
}

 时间交集

public static Map<String, Date> dateIntersec(Date start1, Date end1, Date start2, Date end2) {
		Map<String, Date> dates = new HashMap<String, Date>();
		Date start = new Date();
		Date end = new Date();
		if (start1.after(end1) || start2.after(end2)) {
			return null;
		}
		if (start1.after(end2) || start2.after(end1)) {
			return null;
		}
		if (start1.after(start2)) {
			start = start1;
		} else {
			start = start2;
		}
		if (end1.after(end2)) {
			end = end2;
		} else {
			end = end1;
		}
		dates.put("start", start);
		dates.put("end", end);
		return dates;
	}