Dart-Flutter DateTime日期转换

1.日期转换成时间戳

var now=new DateTime.now();

print(now.millisecondsSinceEpoch); //单位毫秒，13位时间戳

2.时间戳转换成日期

var now=new DateTime.now();

var a=now.millisecondsSinceEpoch; // 时间戳

print(DateTime.fromMillisecondsSinceEpoch(a));

3.创建指定时间 

DateTime assignDay = new DateTime(2020,10,10);

print(assignDay);   // 2020-10-10 00:00:00.000

4.计算时间跨度

// 例如计算1天14小时45分的跨度

Duration timeRemaining = new Duration(days:1, hours:14, minutes:45);

print(timeRemaining);  // 38:45:00.000000

5.字符串转DateTime

DateTime.parse('2019-11-08') 或者 DateTime.parse('2019-11-08 12:30:05')

6.在之前——时间比较

var today = DateTime.now();

var date = DateTime.parse("2019-06-20 15:32:41");

today.isBefore(date);

7.在之后——时间比较

var today = DateTime.now();

var date = DateTime.parse("2019-06-20 15:32:41");

today.isAfter(date);

8.相等——时间比较

var today = DateTime.now();

var date = DateTime.parse("2019-06-20 15:32:41");

today.isAtSameMomentAs(date);

9.时间增加

var today = DateTime.now();   // 2019-11-08 02:54:53.218443

var fiftyDaysFromNow = today.add(new Duration(days: 5));

print('today加5天：$fiftyDaysFromNow');  // today加5天：2019-11-13 02:54:53.218443

10.时间减少

var today = DateTime.now();   // 2019-11-08 02:54:53.218443

var fiftyDaysAgo = today.add(new Duration(days: 5));

print('today加5天：$fiftyDaysAgo ');  // today减5天：2019-11-03 02:54:53.218443

11.时间差(小时数)

var day1 = new DateTime(2019, 6, 20, 17, 30, 20);

var day2 = new DateTime(2019, 7, 21, 0,  0, 0);

print('比较两个时间 差 小时数：${day1.difference(day2)}');  //  比较两个时间 差 小时数：-726:29:40.000000

12.获取年、月、日、星期、时、分、秒、毫秒、微妙

year、month、day、weekday、hour、minute、second、millisecond、microsecond

var today = DateTime.now();

print(today.year);

13.获取本地时区简码

DateTime today = DateTime.now();

print('本地时区简码：${today.timeZoneName}');  //  本地时区简码：GMT

14.返回UTC与本地时差(小时数）

DateTime today = DateTime.now();

print('返回UTC与本地时差 小时数：${today.timeZoneOffset}');