Duration class

A difference between points in time.

A Duration is a signed number of microseconds, which represents an offset from a point in time to another. You can add a Duration to a DateTime, which gives the point in time that is offset by that duration from the original.

Most durations are positive and represent an offset to a later time. A positive duration is useful for representing a delay, a point in the future relative to now (as used by Future.delayed), or as a measure of time that has passed from an earlier time until now (as reported by Stopwatch.elapsed).

A negative duration is the difference from a later time to an earlier, and adding it to a time gives an earlier time. You cannot wait for a negative amount of time using Future.delayed.

Durations are independent of calendars. For example, a duration of 2 days is always 48 hours, even when it is added to a DateTime just when the time zone is about to make a daylight-savings switch. (See DateTime.add).

A duration is a (positive or negative) number of microseconds. Durations are ordered by this number of microseconds when compared using operator < or compareTo.

Despite the same name, a Duration object does not implement "Durations" as specified by ISO 8601. In particular, a duration object does not keep track of the individually provided members (such as "days" or "hours"), but only uses these arguments to compute the length of the corresponding time interval.

To create a new Duration object, use this class's single constructor giving the appropriate arguments:

const fastestMarathon = Duration(hours: 2, minutes: 3, seconds: 2);

The created Duration is defined by the number of microseconds that is the sum of all the individual arguments to the constructor.

Properties can access that single number in different ways. The inMicroseconds is the entire value, and, for example, inMinutes gives the number of whole minutes in the total duration, which includes any minutes that were provided as "hours" to the constructor or provided as "seconds" with a value of 60 or above.

const fastestMarathon = Duration(hours: 2, minutes: 0, seconds: 35);
print(fastestMarathon.inDays); // 0
print(fastestMarathon.inHours); // 2
print(fastestMarathon.inMinutes); // 120
print(fastestMarathon.inSeconds); // 7235
print(fastestMarathon.inMilliseconds); // 7235000

If a duration is negative, all the properties derived from the duration are non-positive (negative unless they are zero).

const overDayAgo = Duration(days: -1, hours: -10);
print(overDayAgo.inDays); // -1
print(overDayAgo.inHours); // -34
print(overDayAgo.inMinutes); // -2040

Use one of the properties, such as inDays, to retrieve the integer value of the Duration in the specified time unit. Note that the returned value is rounded towards zero. For example,

const aLongWeekend = Duration(hours: 88);
print(aLongWeekend.inDays); // 3
const aLongWeekendAgo = Duration(hours: -88);
print(aLongWeekendAgo.inDays); // -3

A duration also provides arithmetic and comparison operators, all based on the microsecond offset of the duration. and the class provides a set of constants useful for converting between time units.

const firstHalf = Duration(minutes: 45); // 00:45:00.000000
const secondHalf = Duration(minutes: 45); // 00:45:00.000000
const overTime = Duration(minutes: 30); // 00:30:00.000000
final maxGameTime = firstHalf + secondHalf + overTime;
print(maxGameTime.inMinutes); // 120

// The duration of the firstHalf and secondHalf is the same, returns 0.
var result = firstHalf.compareTo(secondHalf);
print(result); // 0

// Duration of overTime is shorter than firstHalf, returns < 0.
result = overTime.compareTo(firstHalf);
print(result); // < 0

// Duration of secondHalf is longer than overTime, returns > 0.
result = secondHalf.compareTo(overTime);
print(result); // > 0

See also:

• DateTime to represent a point in time.
• Stopwatch to measure time-spans.