DateTime

2 min read

Use DateTime to represent an instant and display it in UTC or another time zone. Use Duration for a length of time, and Stopwatch to measure how long a task takes.

Import: import system;

An instant in time, shown in UTC or a zone offset. Same package as Time and Stopwatch.

import system;

fun main() {
    let now = DateTime.now();
    System.println(now.year);
    System.println(now.to_string());
}

Build

Call	Meaning
DateTime.now()	current local time
DateTime.utc_now()	current UTC; needs no timezone data
DateTime.of(year, month, day, …)	build from calendar fields
now_in(tz)	current time in a TimeZone
of_zoned(..., tz) / of_local(...)	build in a named zone or the machine local zone
from_epoch_millis / from_epoch_seconds	from Unix epoch

Read

Field / call	Meaning
.year / .month / .day	calendar date
.hour / .minute / .second / .millisecond	time of day
.day_of_week	weekday (0 = Sunday)
.day_of_year	day of year (1-based)

Change

Call	Meaning
to_utc() / to_local() / to_zone(zone)	convert zone
add(Duration.from_days(1L))	shift by any Duration, including a negative one
until(other)	the Duration between two instants
start_of_day()	midnight of that calendar day
is_before / is_after / equals / compare	compare
==, <, and friends	operators

Format and parse

to_string() for a default rendering; to_iso8601() for ISO text. parse (ISO-8601) returns Result.

Duration is a millisecond span. Create one with Duration(millis), from_seconds, from_minutes, from_hours, or from_days; read it with the millis field or as_seconds(); and combine spans with add / sub. DateTime.add(d) and until(other) use it.

TimeZone

Named zones for “what time is it in Tokyo” independent of the machine’s local zone.

Time / Stopwatch

Time.sleep(ms).await / delay(ms) (async, optional last CancellationToken). Time.nano_time() for a monotonic clock. Stopwatch records elapsed time. Also listed under Built-ins.