Time Libraries

This page documents the date/time libraries shipped under lib/time.

These are library classes, not core built-in classes. Load them with intern.

Platform Scope

• time/Date_Time: JVM interpreter, generated JVM, generated JavaScript/Node
• time/Duration: JVM interpreter, generated JVM, generated JavaScript/Node
• Retired browser interpreter path: not supported

Load

intern time/Duration
intern time/Date_Time

Duration

Duration is a time span stored as total milliseconds.

class Duration
create
  milliseconds(ms: Integer64)
  seconds(n: Integer)
  minutes(n: Integer)
  hours(n: Integer)
  days(n: Integer)
  weeks(n: Integer)
feature
  total_milliseconds(): Integer64
  total_seconds(): Real
  plus(other: Duration): Duration
  minus(other: Duration): Duration
  to_string(): String
end

Example:

intern time/Duration

let a: Duration := create Duration.minutes(5)
let b: Duration := create Duration.seconds(30)
print(a.plus(b).total_seconds())

Date_Time

Date_Time is a UTC date-time value stored as epoch milliseconds.

class Date_Time
create
  now()
  from_epoch_millis(ms: Integer64)
  parse_iso(text: String)
  make(year, month, day, hour, minute, second: Integer)
feature
  year(): Integer
  month(): Integer
  month_name(): String
  day(): Integer
  weekday(): Integer
  weekday_name(): String
  day_of_year(): Integer
  hour(): Integer
  minute(): Integer
  second(): Integer
  epoch_millis(): Integer64
  add(duration: Duration): Date_Time
  subtract(duration: Duration): Date_Time
  difference(other: Date_Time): Duration
  truncate_to_day(): Date_Time
  truncate_to_hour(): Date_Time
  is_before(other: Date_Time): Boolean
  is_after(other: Date_Time): Boolean
  format_iso(): String
  to_string(): String
end

Notes: - values are interpreted in UTC - format_iso() returns an ISO-8601 string - difference(other) returns this - other - weekday() uses ISO numbering: 1 = Monday through 7 = Sunday - truncation methods keep the result in UTC

Example:

intern time/Duration
intern time/Date_Time

let start: Date_Time := create Date_Time.make(2026, 3, 13, 10, 30, 0)
let later: Date_Time := start.add(create Duration.hours(2))

print(start.format_iso())
print(start.month_name())
print(start.weekday())
print(start.weekday_name())
print(start.day_of_year())
print(start.truncate_to_day().format_iso())
print(start.truncate_to_hour().format_iso())
print(later.hour())
print(later.difference(start).total_seconds())