Time.DateTime

An exact moment viewed in a timezone. Equality and ordering compare the moment; sameRepresentation also compares the zone identifier. Calendar calculations use the stored zone, so equal moments in different zones can advance to different moments. Viewing a moment in another zone never fails: see Time.Instant for the supported range that makes this so.

add moves by elapsed time; advance moves local calendar fields. Compatible resolution chooses the earlier overlap and moves forward by a gap. Zero adjustments and unchanged field replacements preserve the original moment. ISO output is the local reading with its offset, which parse accepts, so a round trip keeps the moment and the local view but not an IANA zone name: store that identifier separately when the zone must survive serialization.

import Time.DateTime as DT
import Time.Zone as Zone
import Fail
import Result exposing (Result(..))

result = Fail.attempt {
    local = DT.parse "2026-10-07T09:00:00-03:00"
    utc = DT.inZone Zone.utc local
    (DT.toIso utc, local == utc, DT.sameRepresentation local utc)
    }
result == Ok ("2026-10-07T12:00:00Z", True, False)

type DateTimeSource

Eq DateTime
Ord DateTime
Show DateTime

add : Duration -> DateTime ->{Fail Error} DateTimeSource

addDays : Int -> DateTime ->{Fail Error} DateTimeSource

addMonths : Int -> DateTime ->{Fail Error} DateTimeSource

addWeeks : Int -> DateTime ->{Fail Error} DateTimeSource

addYears : Int -> DateTime ->{Fail Error} DateTimeSource

advance : Period -> DateTime ->{Fail Error} DateTimeSource

advanceWith : Resolution -> Period -> DateTime ->{Fail Error} DateTimeSource

beginningOfDay : DateTime ->{Fail Error} DateTimeSource

beginningOfMonth : DateTime ->{Fail Error} DateTimeSource

beginningOfQuarter : DateTime ->{Fail Error} DateTimeSource

beginningOfWeek : DateTime ->{Fail Error} DateTimeSource

beginningOfWeekOn : Weekday -> DateTime ->{Fail Error} DateTimeSource

beginningOfYear : DateTime ->{Fail Error} DateTimeSource

between : DateTime -> DateTime -> DurationSource

date : DateTime -> DateSource

day : DateTime -> IntSource

dayRange : DateTime ->{Fail Error} (DateTime, DateTime)Source

format : String -> DateTime -> StringSource

fromInstant : Zone -> Instant -> DateTimeSource

hour : DateTime -> IntSource

inZone : Zone -> DateTime -> DateTimeSource

make : Zone -> Date -> TimeOfDay ->{Fail Error} DateTimeSource

makeWith : Resolution -> Zone -> Date -> TimeOfDay ->{Fail Error} DateTimeSource

minute : DateTime -> IntSource

month : DateTime -> IntSource

monthRange : DateTime ->{Fail Error} (DateTime, DateTime)Source

nanosecond : DateTime -> IntSource

offsetSeconds : DateTime -> IntSource

parse : String ->{Fail Error} DateTimeSource

quarterRange : DateTime ->{Fail Error} (DateTime, DateTime)Source

sameRepresentation : DateTime -> DateTime -> BoolSource

second : DateTime -> IntSource

startOfDay : Zone -> Date ->{Fail Error} DateTimeSource

timeOfDay : DateTime -> TimeOfDaySource

toInstant : DateTime -> InstantSource

toIso : DateTime -> StringSource

weekday : DateTime -> WeekdaySource

weekRange : DateTime ->{Fail Error} (DateTime, DateTime)Source

withDate : Date -> DateTime ->{Fail Error} DateTimeSource

withDateWith : Resolution -> Date -> DateTime ->{Fail Error} DateTimeSource

withTime : TimeOfDay -> DateTime ->{Fail Error} DateTimeSource

withTimeWith : Resolution -> TimeOfDay -> DateTime ->{Fail Error} DateTimeSource

year : DateTime -> IntSource

yearRange : DateTime ->{Fail Error} (DateTime, DateTime)Source

zone : DateTime -> ZoneSource