The Swim Time library implements date-time, time zone, and time interval data
types, with strptime
/strftime
-style parsers and formatters. The Swim Time
library facilitates parsing and formatting of date strings, time zone aware
date manipulation, and sampling of date ranges at regular time intervals.
The DateTime
class models an immutable instant in time, relative to a
particular TimeZone
. The DateTime.current
static method returns the
current time in the local time zone, or in an optionally specified time zone.
DateTime.current();
DateTime.current(TimeZone.utc());
The DateTime.fromInit
static method coerces plain JavaScript objects, of type
DateTimeInit
, to instances of DateTime
. DateTime.fromInit
defaults to UTC,
but can optionally be passed a specific time zone.
DateTime.fromInit({year: 2019});
// "2019-01-01T00:00:00.000Z"
DateTime.fromInit({year: 2019, month: 8, day: 12, hour: 5, minute: 16, second: 10});
// "2019-09-12T05:16:10.000Z"
DateTime.fromInit({year: 2019, month: 8, day: 12, hour: 5, minute: 16, second: 10}, TimeZone.local());
// "2019-09-11T15:16:10.000Z"
The DateTime.fromLike
static method coerces common JavaScript date
representations, including ECMAScript Date
objects, numbers representing
milliseconds since the Unix epoch, and ISO 8601-formatted date-time strings,
to DateTime
instances.
DateTime.fromLike(Date.now());
// "2019-08-12T22:54:39.648Z"
DateTime.fromLike(1565650479648);
// "2019-08-12T22:54:39.648Z"
DateTime.fromLike("2019-08-12T22:54:39.648Z");
// "2019-08-12T22:54:39.648Z"
The TimeZone
class represents an immutable offset, in minutes, from Universal
Coordinated Time (UTC). The TimeZone.local()
and TimeZone.utc()
static
methods return the current local time zone, and the UTC time zone, respectively.
TimeZone.local();
// TimeZone.forOffset(-420)
TimeZone.utc();
// TimeZone.forOffset(0)
A DateTimeFormat
represents a string encoding that parse date-time strings
as DateTime
objects, and format DateTime
objects as date-time strings.
The DateTimeFormat.iso8601()
static method returns the standard ISO 8601
date-time format. The DateTimeFormat.pattern
method returns a
DateTimeFormat
that parses and formats date-times according to a
strptime
/strftime
-style format string.
Use the parse
method of a DateTimeFormat
to parse a DateTime
object from
a compatible date-time string:
DateTimeFormat.iso8601().parse("2019-08-12T16:11:59.586Z");
// "2019-08-12T16:11:59.586Z
DateTimeFormat.pattern("%Y-%m-%d").parse("2019-08-12");
// "2019-08-12T00:00:00.000Z"
DateTimeFormat.pattern("%H:%M:%S").parse("16:11:59");
// "1970-01-01T16:11:59.000Z"
Use the format
method of a DateTimeFormat
to serialize a DateTime
object
to a compatible date-time string. You can also optionally pass a
DateTimeFormat
to a DateTime
's toString
method.
DateTimeFormat.iso8601().format(DateTime.current());
// "2019-08-12T16:15:27.045Z"
DateTime.current().toString(DateTimeFormat.pattern("%Y-%m-%d"));
// "2019-08-12"
DateTime.current().toString(DateTimeFormat.pattern("%H:%M:%S"));
// "16:16:20"
DateTime.current().toString(DateTimeFormat.pattern("%b %d"));
// "Aug 12"
A DateTimeLocale
specifies the period, weekday, short weekday, month, and
short month strings used when parsing and formatting date-time strings.
DateTimeLocale.standard()
returns the standard English language locale.
A TimeInterval
represents a regular duration of time. A UnitTimeInterval
represents a time interval with a uniform duration. Milliseconds, seconds,
minutes, hours, and days are unit time intervals. Weeks, months, and years
are not unit time intervals, because different weeks, months, and years can
have different durations.
Time intervals can be created with the TimeInterval.millisecond
,
TimeInterval.second
, TimeInterval.minute
, TimeInterval.hour
,
TimeInterval.day
, TimeInterval.week
, TimeInterval.month
, and
TimeInterval.year
factory methods.
A TimeInterval
can be used to offset
a DateTime
by a multiple of the
interval, to advance to the next
whole multiple of the interval, to round
a DateTime
down to the floor
of the interval, to round a DateTime
up
to the ceil
of the interval, or to round
a DateTime
to the nearest
whole interval.
TimeInterval.second.offset("2019-08-12T16:35:10.838Z", 5);
// "2019-08-12T16:35:15.838Z"
TimeInterval.minute.next("2019-08-12T16:35:10.838Z");
// "2019-08-12T16:36:00.000Z"
TimeInterval.minute.next("2019-08-12T16:35:10.838Z", 30);
// "2019-08-12T17:05:00.000Z"
TimeInterval.hour.floor("2019-08-12T16:35:10.838Z");
// "2019-08-12T16:00:00.000Z"
TimeInterval.day.ceil("2019-08-12T16:35:10.838Z");
// "2019-08-13T00:00:00.000Z"
TimeInterval.week.round("2019-08-12T16:35:10.838Z");
// "2019-08-11T00:00:00.000Z"
The every
method of a UnitTimeInterval
returns a new TimeInterval
equal
to a multiple of the base time interval.
TimeInterval.minute.every(15).next("2019-08-12T16:35:10.838Z");
// "2019-08-12T16:45:00.000Z"
The range
method of a TimeInterval
returns an array of DateTime
s
representing every whole interval between some start time (inclusive), and
some end time (exclusive). An optional third argument to range
indicates
that only every step
multiple of the base interval should be included in
the returned range.
The TimeInterval.milliseconds
, TimeInterval.seconds
, TimeInterval.minutes
,
TimeInterval.hours
, TimeInterval.days
, TimeInterval.weeks
,
TimeInterval.months
, and TimeInterval.years
factory methods provide
a shorthand for computing a range of DateTime
s between two times, and
return the equivalent of calling range
on the underlying time interval.
TimeInterval.year.range({year: 2017}, {year: 2020});
// ["2017-01-01T00:00:00.000Z", "2018-01-01T00:00:00.000Z", "2019-01-01T00:00:00.000Z"]
TimeInterval.months({year: 2019, month: 3}, {year: 2019, month: 6});
// ["2019-04-01T00:00:00.000Z", "2019-05-01T00:00:00.000Z", "2019-06-01T00:00:00.000Z"]
TimeInterval.days({year: 2019, month: 7, day: 1}, {year: 2019, month: 7, day: 12}, 4);
// ["2019-08-01T00:00:00.000Z", "2019-08-05T00:00:00.000Z", "2019-08-09T00:00:00.000Z"]
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