var d1 = new DateTime(2018, 10, 1);
var d2 = new DateTime(2018, 10, 10);
print(d1.isAfter(d2));
print(d1.isBefore(d2));
var d1 = DateTime.now();
var d2 = d1.add(new Duration(milliseconds: 30));
print(d1.isAtSameMomentAs(d2));
时间差
var d1 = new DateTime(2018, 10, 1);
var d2 = new DateTime(2018, 10, 10);
var difference = d1.difference(d2);
print([difference.inDays, difference.inHours]);
时间戳
var now = new DateTime.now();
print(now.millisecondsSinceEpoch);
print(now.microsecondsSinceEpoch);