In the documentation of

LocalDate.atTime

:

For finding an instant that corresponds to the start of a date in a particular time zone, consider using LocalDate.atStartOfDayIn function because a day does not always start at the fixed time 00000.

Out of curiosity, does that regularly happen? If it was a one-time thing, I'm curious when and why

Hi, I just want to share that I’ve published version 0.3.0 of Cardiologist which accounts for Clock drift now 🙂 Let me know what you think!

Is there a way to format a

LocalDate

without showing the year? Equivalent of Android’s

DateUtils.FORMAT_NO_YEAR

Is there a publicly accessible repo with dev builds of kotlinx-datetime? I'm interested in the new

wasmWasi

target support.

Is this normal?

e: KLIB resolver: Could not find "org.jetbrains.kotlinx:kotlinx-datetime-cinterop-date" in [/…/pedestal, /…/.konan/klib, /…/.konan/kotlin-native-prebuilt-linux-x86_64-2.0.0/klib/common, /…/.konan/kotlin-native-prebuilt-linux-x86_64-2.0.0/klib/platform/linux_x64]

It just started happening on an existing project. Kotlin 2.0.0 KotlinX.Datetime 0.6.0

Hello, does format ISO8601:2004 is supported ?

Hi all. I'm trying to understand an issue: I take local time and with

.toInstant(TimeZone.UTC)

I'm converting it to UTC. I noticed that the time is kept the same. I was expecting it to change to a time in UTC timezone. This creates a disparity between the user creating data in their timezone and expecting it to show up with the same time (when converted back from UTC into system's timezone) however this is not the case as the time is not adjusted. Am I missing something?

I want to create an instance of

kotlinx.datetime.format.DateTimeFormat

which will correctly parse "an iCalendar format DATE-TIME value in UTC". For example

19000101T000000Z

. ChatGPT and Github Copilot are eager to tell me how to do it with Java, but completely lost with Kotlinx datetime.

Hi all. I'm trying to convert an instant from local time zone (e.g. America/New_York) to UTC (with offset) which should be (at this moment in time) +5 hours. When I'm trying to calculate offset in time zone UTC I get no change (printing it shows "Z"). How can I convert from local time zone adjusted to UTC where the delta is taken into account properly? It seems right now, whatever the instant is it will just be used as is but with UTC with no datetime change.

Hi folks. Any ideas as to why

Clock.System.now().toEpochMilliseconds()

returns time in UTC rather than local time? What was the rationale behind this behaviour?

I have a specific

Instant

. For a given

TimeZone

(thus I can get a

LocalDateTime

), I want to know the very first existing hour of the next day in that timezone. For example, if I have 23h47 december 17th in France, I want 00h00 december 18th. If 00h00 december 18th doesn't exist for whatever reason, I want the very next time that happens in that timezone, however later it happens to be. How can I represent this?

yyyy-MM-dd'T'HHmmss'Z The default formatters or adapters for kotlinx serialization doesnt understand this UTC format used. I often fall back to Instant but ideally I want LocalDateTime. How do I do this the right way if any? I dont like using Instant and want avoid do custom parser. Want standard iso parsers from kotlinx only ideally.

How can I have my custom DateTimeFormat consume a string but return a different value during parsing? I'm trying to add support for leap seconds (

23:59:60

) which needs to subtract one second (becoming

23:59:59

). I have a function:

private fun WithTime.secondOrleapSecond() = alternativeParsing({ second() }) { chars("60") }

. This can parse the leap seconds without crashing, but (understandably) returns

23:59:0

. How can I set

seconds = 59

in this case? I found a GitHub issue about leap seconds, there was a hint of a solution but none offered.

I've seen this question asked before but I don't think I've seen an official answer. Is it intended that

TimeZone.UTC

is not equivalent to

TimeZone.of("UTC")

? That's incredibly unintuitive.

Perhaps relevant to crosspost this here, too: https://kotlinlang.slack.com/archives/C0B8Q383C/p1736968593656649

I have an Instant, and I want to format that to a localized month+year string. So in English, "January 2025", or in Korean "2025년 1월" etc... I know the user's locale, so no magic involved. Feels like this should be very achievable, but can't find any documentation/resources on how to do so in Kotlin multiplatform?

If I want to truncate an Instant to only include up till the hour's start (w/o minutes/seconds/etc...) what's the simplest/most ideomatic way to do this in KotlinX Datetime?

The README says:

DatePeriod

is a subclass of

DateTimePeriod

with zero time components, it represents a difference between two LocalDate values decomposed into date units.

Ok, but, how?

LocalDate

doesn't have a

-

operator 🤔

Is there a reason

UtcOffset

doesn't internally rely on

Duration

? Looking at the code, my guess is that it was to rely on Java's implementation?

Do you have any plans to release a pre release using 2.1.20-Beta2 to use the stdlib Instant class?

📣 kotlinx-datetime 0.6.2 is here, and with it, Wasm/WASI support, along with some small tweaks and fixes! Full changelog: https://github.com/Kotlin/kotlinx-datetime/releases/tag/v0.6.2

Google just introduced a new API to provide a trusted time source https://android-developers.googleblog.com/2025/02/trustedtime-api-introducing-reliable-approach-to-time-keeping-for-apps.html?m=1. Is there a way to use it with kotlinx-datetime?

When can we expect support for Kotlin 2.1 on kotlinx datetime? Not having this holds us back form upgrading all our multiplatfrom projects to Kotlin 2.x. So this is very much needed and will be highly appreciated! Any timeline in sight? @Dmitry Khalanskiy [JB]

Do I understand correctly that the formatting APIs introduced in kotlinx-datetime v0.6 do not format according to the locale? For example they don't display month names or week names according to the current locale, is that correct?

If I get a String like for example

2025-03-24T08:00:00.000001Z

Which indicates that it's in UTC time, hence the

Z

afaik But I may get an instant which is not

Z

there, but some other timezone too Is there a way for me to turn it into a LocalDateTime, but using whatever time-zone the string itself already came in? So I want to do

Instant
 .parse("2025-03-24T08:00:00.000001Z")
 .toLocalDateTime(???)

But not sure what I should do for timezone. The use-case is that my server is giving me a timestamp, and I want to show the date only as-is, so whatever the server had decided already. So if you are in different parts of the world you do not get different results (if I used

TimeZone.currentSystemDefault()

) but I also don't want to just default to UTC and potentially change the date that I show if the timestamp was not in UTC.

Hello everybody! How can I get the current LocalDateTime in Swift using KMP? All I have in Swift for now is something like

Kotlinx_datetimeLocalDateTime

When using

kotlinx-datetime

on Kotlin/JS on Windows I have a strange problem with casing. There is a webpack warning and the library is not working correctly (

ClassCastException

is thrown):

There are multiple modules with names that only differ in casing.
This can lead to unexpected behavior when compiling on a filesystem with other case-semantic.
Use equal casing. Compare these module identifiers:

    javascript/esm|C:\Users\kpadarz\Desktop\Wykaz\wykaz2\wykaz\build\js\packages\wykaz\kotlin\Kotlin-DateTime-library-kotlinx-datetime\kotlinx\datetime\serializers\LocalTimeSerializers.mjs Used by 1 module(s), i. e. javascript/esm|C:\Users\kpadarz\Desktop\Wykaz\wykaz2\wykaz\build\js\packages\wykaz\kotlin\Kotlin-DateTime-library-kotlinx-datetime\kotlinx\datetime\localtime.mjs
    javascript/esm|C:\Users\kpadarz\Desktop\Wykaz\wykaz2\wykaz\build\js\packages\wykaz\kotlin\kotlin-datetime-library-kotlinx-datetime\kotlinx\datetime\serializers\LocalTimeSerializers.mjs Used by 1 module(s), i. e. javascript/esm|C:\Users\kpadarz\Desktop\Wykaz\wykaz2\wykaz\build\js\packages\wykaz\kotlin\kotlin-datetime-library-kotlinx-datetime\kotlinx\datetime\localtime.mjs

I find myself somewhat frequently doing:

val min = LocalTime(hour = 0, minute = 0, second = 0, nanosecond = 0)
val max = LocalTime(hour = 23, minute = 59, second = 59, nanosecond = 999_999_999)

Would there be any interest in accepting a PR that specifies

LocalTime.MIN

and

LocalTime.MAX

like both Instant and LocalDateTime have?

I’m wondering if any of the kotlinx-datetime maintainers have read Jesse’s blog post titled Identifiers aren’t services in which he argues in part that

kotlinx.datetime.TimeZone

shouldn’t query the underlying database from the tzdb entry when calling

TimeZone.of(String)

. Do you have thoughts?

I maintain a (not yet stable) library that exposes extension functions on

kotlinx.datetime.Clock

. I suspect I should move those to

kotlin.time.Clock

? When is

kotlinx.datetime.Clock

planned to be removed?