SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Calendar c = Calendar.getInstance();
1.過去七天
c.setTime(new Date());
c.add(Calendar.DATE, - 7);
Date d = c.getTime();
String day = format.format(d);
System.out.println("過去七天："+day);
2.過去一月
c.setTime(new Date());
c.add(Calendar.MONTH, 
 
-1);
Date m = c.getTime();
String mon = format.format(m);
System.out.println("過去一個月："+mon);
3.過去三個月
c.setTime(new Date());
c.add(Calendar.MONTH, -3);
Date m3 = c.getTime();
String mon3 = format.format(m3);
System.out.println("過去三個月："+mon3);
4.過去一年
c.setTime(new Date());
c.add(Calendar.YEAR, -1);
Date y 
 
= c.getTime();
String year = format.format(y);
System.out.println("過去一年："+year);
5.現在時間24小時制  
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  
String nowDate=format.format(new Date());  
System.out.println(nowDate);  
6.當天的開始時間  
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.當天的截止時間  
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.當前時間的前一個星期 開始時間  
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.當天日期前一個月  
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  
Calendar c = Calendar.getInstance();  
c.add(Calendar.MONTH, -1);    //得到前一個月    
String start = format.format(c.getTime())+" 00:00:00";  
System.out.println(start);  
10.當前時間的前一年開始時間  
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  
Calendar c = Calendar.getInstance();  
c.add(Calendar.YEAR, -1); //年份減1   
String start =format.format(c.getTime())+" 00:00:00";  
System.out.println(start);  
11.當前時間的週一時間和週末時間 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.當前時所在月份的第一天和最後一天  
SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");  
Calendar c = Calendar.getInstance();      
c.set(Calendar.DAY_OF_MONTH,1);//設定為1號,當前日期既為本月第一天   
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.當期時間所在年份的開始時間  
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  
Calendar c = Calendar.getInstance();  
c.set(c.get(Calendar.YEAR) ,0, 1);//開始時間日期  
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));//結束日期  
String yearEnd = format.format(ca.getTime())+" 23:59:59";  
System.out.println(yearEnd);  
14.計算時間差取得兩個時間的微秒級的時間差
//得微秒級時間差    
long val = calendarEnd.getTimeInMillis() - calendarBegin.getTimeInMillis();    
//換算後得到天數    
long day = val / (1000 * 60 * 60 * 24);
15.獲取某個時間的上週一和週日
Calendar cal = Calendar.getInstance();
//n為推遲的週數，1本週，-1向前推遲一週，2下週，依次類推
int n = 1;
String monday;
cal.add(Calendar.DATE, n*7);
//想周幾，這裡就傳幾Calendar.MONDAY（TUESDAY...）
cal.set(Calendar.DAY_OF_WEEK,Calendar.MONDAY);
monday = new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime());
System.out.println(monday);

轉載:https://blog.csdn.net/qq_41040268/article/details/79666263