An instant in time, such as July 20, 1969, 8:18pm GMT.

DateTimes can represent time values that are at a distance of at most 100,000,000 days from epoch (1970-01-01 UTC): -271821-04-20 to 275760-09-13.

Create a DateTime object by using one of the constructors or by parsing a correctly formatted string, which complies with a subset of ISO 8601. Note: hours are specified between 0 and 23, as in a 24-hour clock.

For example:

final now = DateTime.now();
final berlinWallFell = DateTime.utc(1989, 11, 9);
final moonLanding = DateTime.parse('1969-07-20 20:18:04Z'); // 8:18pm
A DateTime object is anchored either in the UTC time zone
or in the local time zone of the current computer
when the object is created.
Once created, neither the value nor the time zone
of a DateTime object may be changed.
You can use properties to get
the individual units of a DateTime object.
print(berlinWallFell.year); // 1989
print(berlinWallFell.month); // 11
print(berlinWallFell.day); // 9
print(moonLanding.hour); // 20
print(moonLanding.minute); // 18
For convenience and readability,
the DateTime class provides a constant for each day and month
name - for example, august and friday.
You can use these constants to improve code readability:
final berlinWallFell = DateTime.utc(1989, DateTime.november, 9);
print(DateTime.november); // 11
assert(berlinWallFell.month == DateTime.november);
assert(berlinWallFell.weekday == DateTime.thursday);
Day and month values begin at 1, and the week starts on Monday.
That is, the constants january and monday are both 1.
Working with UTC and local time
A DateTime object is in the local time zone
unless explicitly created in the UTC time zone.
Use isUtc to determine whether a DateTime object is based in UTC.
final dDay = DateTime.utc(1944, 6, 6);
print(dDay.isUtc); // true
final dDayLocal = DateTime(1944, 6, 6);
print(dDayLocal.isUtc); // false
Use the methods toLocal and toUtc
to get the equivalent date/time value specified in the other time zone.
final localDay = dDay.toLocal(); // e.g. 1944-06-06 02:00:00.000
print(localDay.isUtc); // false
final utcFromLocal = localDay.toUtc(); // 1944-06-06 00:00:00.000Z
print(utcFromLocal.isUtc); // true
Use timeZoneName to get an abbreviated name of the time zone
for the DateTime object.
print(dDay.timeZoneName); // UTC
print(localDay.timeZoneName); // e.g. EET
To find the difference
between UTC and the time zone of a DateTime object
call timeZoneOffset.
print(dDay.timeZoneOffset); // 0:00:00.000000
print(localDay.timeZoneOffset); // e.g. 2:00:00.000000
Comparing DateTime objects
The DateTime class contains methods for comparing DateTimes
chronologically, such as isAfter, isBefore, and isAtSameMomentAs.
print(berlinWallFell.isAfter(moonLanding)); // true
print(berlinWallFell.isBefore(moonLanding)); // false
print(dDay.isAtSameMomentAs(localDay)); // true
Using DateTime with Duration
Use the add and subtract methods with a Duration object
to create a DateTime object based on another.
For example, to find the point in time that is 36 hours after now,
you can write:
final now = DateTime.now();
final later = now.add(const Duration(hours: 36));
To find out how much time is between two DateTime objects use
difference, which returns a Duration object:
final difference = berlinWallFell.difference(moonLanding);
print(difference.inDays); // 7416
The difference between two dates in different time zones
is just the number of nanoseconds between the two points in time.
It doesn't take calendar days into account.
That means that the difference between two midnights in local time may be
less than 24 hours times the number of days between them,
if there is a daylight saving change in between.
If the difference above is calculated using Australian local time, the
difference is 7415 days and 23 hours, which is only 7415 whole days as
reported by inDays.
Other resources
See Duration to represent a span of time.
See Stopwatch to measure timespans.
The DateTime class does not provide internationalization.
 To internationalize your code, use
 the intl package.
          DateTime(int year, [int month = 1, int day = 1, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0])
          Constructs a DateTime instance specified in the local time zone.
          DateTime.fromMicrosecondsSinceEpoch(int microsecondsSinceEpoch, {bool isUtc = false})
          Constructs a new DateTime instance
with the given microsecondsSinceEpoch.
          DateTime.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch, {bool isUtc = false})
          Constructs a new DateTime instance
with the given millisecondsSinceEpoch.
          DateTime.now()
          Constructs a DateTime instance with current date and time in the
local time zone.
          DateTime.timestamp()
          Constructs a DateTime with the current UTC date and time.
          DateTime.utc(int year, [int month = 1, int day = 1, int hour = 0, int minute = 0, int second = 0, int millisecond = 0, int microsecond = 0])
          Constructs a DateTime instance specified in the UTC time zone.
  Returns true if other is a DateTime at the same moment and in the
same time zone (UTC or local).
  
override