# DateTime class

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 that hours are specified between 0 and 23, as in a 24-hour clock. For example:

    var now = new DateTime.now();
    var berlinWallFell = new DateTime.utc(1989, 11, 9);
    var 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.

    assert(berlinWallFell.month == 11);
    assert(moonLanding.hour == 20);

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:

    var berlinWallFell = new DateTime.utc(1989, DateTime.november, 9);
    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.

    var dDay = new DateTime.utc(1944, 6, 6);

Use isUtc to determine whether a DateTime object is based in UTC. Use the methods toLocal and toUtc to get the equivalent date/time value specified in the other time zone. Use timeZoneName to get an abbreviated name of the time zone for the DateTime object. To find the difference between UTC and the time zone of a DateTime object call timeZoneOffset.

## Comparing DateTime objects

The DateTime class contains several handy methods, such as isAfter, isBefore, and isAtSameMomentAs, for comparing DateTime objects.

    assert(berlinWallFell.isAfter(moonLanding) == true);
    assert(berlinWallFell.isBefore(moonLanding) == false);

## Using DateTime with Duration

Use the add and subtract methods with a Duration object to create a new DateTime object based on another. For example, to find the date that is sixty days (24 * 60 hours) after today, write:

    var now = new DateTime.now();
    var sixtyDaysFromNow = now.add(new Duration(days: 60));

To find out how much time is between two DateTime objects use difference, which returns a Duration object:

    var difference = berlinWallFell.difference(moonLanding);
    assert(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.

Implements
  - Comparable<DateTime>

## Constructors

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.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. [...]

## Properties

day → int
  The day of the month `1..31`. [...]
  read-only
hashCode → int
  The hash code for this object. [...]
  read-only
hour → int
  The hour of the day, expressed as in a 24-hour clock `0..23`. [...]
  read-only
isUtc → bool
  True if this `DateTime` is set to UTC time. [...]
  final
microsecond → int
  The microsecond `0...999`. [...]
  read-only
microsecondsSinceEpoch → int
  The number of microseconds since the "Unix epoch" 1970-01-01T00:00:00Z (UTC). [...]
  read-only
millisecond → int
  The millisecond `0...999`. [...]
  read-only
millisecondsSinceEpoch → int
  The number of milliseconds since the "Unix epoch" 1970-01-01T00:00:00Z (UTC). [...]
  read-only
minute → int
  The minute `0...59`. [...]
  read-only
month → int
  The month `1..12`. [...]
  read-only
second → int
  The second `0...59`. [...]
  read-only
timeZoneName → String
  The time zone name. [...]
  read-only
timeZoneOffset → Duration
  The time zone offset, which is the difference between local time and UTC. [...]
  read-only
weekday → int
  The day of the week monday..sunday. [...]
  read-only
year → int
  The year. [...]
  read-only
runtimeType → Type
  A representation of the runtime type of the object.
  read-only, inherited

## Methods

add(Duration duration) → DateTime
  Returns a new DateTime instance with `duration` added to this. [...]
compareTo(DateTime other) → int
  Compares this DateTime object to `other`, returning zero if the values are equal. [...]
difference(DateTime other) → Duration
  Returns a Duration with the difference between this and `other`. [...]
isAfter(DateTime other) → bool
  Returns true if this occurs after `other`. [...]
isAtSameMomentAs(DateTime other) → bool
  Returns true if this occurs at the same moment as `other`. [...]
isBefore(DateTime other) → bool
  Returns true if this occurs before `other`. [...]
subtract(Duration duration) → DateTime
  Returns a new DateTime instance with `duration` subtracted from this. [...]
toIso8601String() → String
  Returns an ISO-8601 full-precision extended format representation. [...]
toLocal() → DateTime
  Returns this DateTime value in the local time zone. [...]
toString() → String
  Returns a human-readable string for this instance. [...]
toUtc() → DateTime
  Returns this DateTime value in the UTC time zone. [...]
noSuchMethod(Invocation invocation) → dynamic
  Invoked when a non-existent method or property is accessed. [...]
  inherited

## Operators

operator ==(dynamic other) → bool
  Returns true if `other` is a DateTime at the same moment and in the same time zone (UTC or local). [...]

## Static Methods

parse(String formattedString) → DateTime
  Constructs a new DateTime instance based on `formattedString`. [...]
tryParse(String formattedString) → DateTime

## Constants

april → const int
  `4`
august → const int
  `8`
daysPerWeek → const int
  `7`
december → const int
  `12`
february → const int
  `2`
friday → const int
  `5`
january → const int
  `1`
july → const int
  `7`
june → const int
  `6`
march → const int
  `3`
may → const int
  `5`
monday → const int
  `1`
monthsPerYear → const int
  `12`
november → const int
  `11`
october → const int
  `10`
saturday → const int
  `6`
september → const int
  `9`
sunday → const int
  `7`
thursday → const int
  `4`
tuesday → const int
  `2`
wednesday → const int
  `3`