SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

Calendar c = Calendar.getInstance();

1.过去七天

c.setTime(new Date());

c.add(Calendar.DATE, - 7);

Date d = c.getTime();

String day = format.format(d);

System.out.println("过去七天："+day);

2.过去一月

c.setTime(new Date());

c.add(Calendar.MONTH, -1);

Date m = c.getTime();

String mon = format.format(m);

System.out.println("过去一个月："+mon);

3.过去三个月

c.setTime(new Date());

c.add(Calendar.MONTH, -3);

Date m3 = c.getTime();

String mon3 = format.format(m3);

System.out.println("过去三个月："+mon3);

4.过去一年

c.setTime(new Date());

c.add(Calendar.YEAR, -1);

Date y = c.getTime();

String year = format.format(y);

System.out.println("过去一年："+year);

5.现在时间24小时制  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  

String nowDate=format.format(new Date());  

System.out.println(nowDate);  

6.当天的开始时间  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();  

String start = format.format(c.getTime())+" 00:00:00";  

System.out.println(start);  

7.当天的截止时间  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar calendar = Calendar.getInstance();  

String end = format.format(calendar.getTime())+" 23:59:59";  

System.out.println(end);  

8.当前时间的前一个星期 开始时间  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();  

c.add(Calendar.DAY_OF_MONTH, -6);  

String start = format.format(c.getTime())+" 00:00:00";  

System.out.println(start);  

9.当天日期前一个月  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();  

c.add(Calendar.MONTH, -1);    //得到前一个月    

String start = format.format(c.getTime())+" 00:00:00";  

System.out.println(start);  

10.当前时间的前一年开始时间  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();  

c.add(Calendar.YEAR, -1); //年份减1   

String start =format.format(c.getTime())+" 00:00:00";  

System.out.println(start);  

11.当前时间的周一时间和周末时间 setfirstdayofweek（）方法  

SimpleDateFormat format  = new SimpleDateFormat("YYYY-MM-dd ");  

Calendar c = Calendar.getInstance();  

c.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY);  

String weekStart = format.format(c.getTime())+" 00:00:00";  

System.out.println(weekStart);  

Calendar ca = Calendar.getInstance();  

ca.setFirstDayOfWeek(Calendar.MONDAY);  

ca.set(Calendar.DAY_OF_WEEK, ca.getFirstDayOfWeek() + 6); // Sunday  

String weekEnd = format.format(ca.getTime())+" 23:59:59";  

System.out.println(weekEnd);  

12.当前时所在月份的第一天和最后一天  

SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();      

c.set(Calendar.DAY_OF_MONTH,1);//设置为1号,当前日期既为本月第一天   

String monthStart = format.format(c.getTime())+" 00:00:00";  

System.out.println(monthStart);  

Calendar ca = Calendar.getInstance();      

ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));    

String monthEnd = format.format(ca.getTime())+" 23:59:59";  

System.out.println(monthEnd);  

13.当期时间所在年份的开始时间  

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

Calendar c = Calendar.getInstance();  

c.set(c.get(Calendar.YEAR) ,0, 1);//开始时间日期  

String yearStart = format.format(c.getTime())+" 00:00:00";  

System.out.println(yearStart);  

Calendar ca = Calendar.getInstance();  

ca.set(ca.get(Calendar.YEAR) ,11, ca.getActualMaximum(Calendar.DAY_OF_MONTH));//结束日期  

String yearEnd = format.format(ca.getTime())+" 23:59:59";  

System.out.println(yearEnd);  

14.计算时间差取得两个时间的微秒级的时间差

//得微秒级时间差    

long val = calendarEnd.getTimeInMillis() - calendarBegin.getTimeInMillis();    

//换算后得到天数    

long day = val / (1000 * 60 * 60 * 24);

15.获取某个时间的上周一和周日

Calendar cal = Calendar.getInstance();

//n为推迟的周数，1本周，-1向前推迟一周，2下周，依次类推

int n = 1;

String monday;

cal.add(Calendar.DATE, n*7);

//想周几，这里就传几Calendar.MONDAY（TUESDAY...）

cal.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY);

monday = new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime());

System.out.println(monday);