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?

Hey, DayOfWeek in Android is typealiased to java.time, so it require API26 or there is a built in desugaring ?

📣

kotlinx-datetime

0.7.0 is here! •

Instant

and

Clock

were moved to the standard library and are no longer part of

kotlinx-datetime

. Please follow https://github.com/Kotlin/kotlinx-datetime?tab=readme-ov-file#deprecation-of-instant if you encounter problems because of that. •

LocalDateRange

, a range of date values, was added. •

YearMonth

and

YearMonthRange

were added. • Serializers that can be parameterized with a

DateTimeFormat

were added. • Most entities in the library are

java.io.Serializable

now. • Other changes. The full changelog is available here: https://github.com/Kotlin/kotlinx-datetime/releases/tag/v0.7.0

If you are 1. Not using libraries that themselves depend on

kotlinx-datetime

0.6.2 or earlier, and are also 2. Planning on upgrading to

kotlinx-datetime

0.7.0, but haven't yet, then you are advised to wait until 0.7.1 comes out in the next few days. 0.7.0 is missing some migration assistance, namely the deprecated-with-warning type aliases

kotlinx.datetime.Instant = kotlin.time.Instant

and

kotlinx.datetime.Clock = kotlin.time.Clock

(https://github.com/Kotlin/kotlinx-datetime/pull/540/commits/f829958a1bcbe7b24a11a91519cf57aaf3daa74b). Without them, your client code will not compile until you replace the usages manually, whereas with them, you will be able to proceed at your own pace (if you are not using libraries that themselves depend on

kotlinx.datetime.Instant

) or even perform automatic replacement with the help of an IDE. This is a glaring omission that I made when publishing the release, and I am sorry about that. The type aliases in 0.7.0 were planned from the beginning, but due to my oversight, were missing from the release.

📣

kotlinx-datetime

0.7.1 is here, providing a more convenient migration path to

kotlin.time.Instant

! https://github.com/Kotlin/kotlinx-datetime/releases/tag/v0.7.1

Are prebuilt auto-internationalized local date time formatters coming (like

java.time

has)?

If I understand correctly,

kotlin.time.Instant

and

kotlin.time.Clock

were introduced in Kotlin 2.1.20 Then, kotlinx.serialization added support for these 2 types in v1.9.0, but that requires Kotlin 2.2 What are my options if I want to stay on Kotlin 2.1.20 and want to serialize kotlin.time.Instant types? Is the

compat

artifact useful for this situation?

kotlinx.datetime.Instant

would be visible to iOS as

Kotlinx_datetimeInstant

Since it is moved to the stdlib, what should it be exported as?

Kotlin_timeInstant

is not found, neither is just Instant.

📣 Hi everyone! A heads-up: we are planning to remove the

@Serializable

annotation from

TimeZone

and

FixedOffsetTimeZone

in the future and deprecate the serializers for these classes. Please restructure your code to send and receive the timezone identifier (

timeZone.id

, converted back to the timezone with

TimeZone.of(id)

) instead of the timezone itself. The reason for this change is that the timezone database used in the code performing the deserialization can be different from the one that was used for serialization. This may even lead to crashes if the deserializing side does not know the serialized timezone identifier. The explicit need to call

TimeZone.of

on the deserialization result gives a more controlled environment for handling the failure and demonstrates the risk better.

Hey folks! We're thinking about

kotlin.time.Instant

and

kotlin.time.Clock

stabilization in Kotlin

2.3

, so if there was anything with them that you wanted to change, it's time to let us know: https://kotlinlang.slack.com/archives/C0B8Q383C/p1755279531599069

Does anyone have any suggestions for dealing with errors like this? > org.apache.fury.exception.InsecureException: class kotlin.time.InstantSerialized is not registered... Basically, a serialization library wants me to register

InstantSerialized::class.java

because I use

kotlin.time.Instant

in a data class but I can't because

InstantSerialized

is private. I did not have this problem with

kotlinx-datetime

.

Hi all! I'm updating to version

0.7.1

of the datetime library, and I'm getting an error. I have read the docs about the Dreprecation of `Instant`, so I'm familiar with updates that need to happen there. I'm using

Clock

and have updated to

import kotlin.time.Clock

. But I get an error (in the IDE and at compile): > This declaration is only available in Kotlin 2.1 and newer versions and cannot be used with the specified API version 2.0. I'm confused by this as I'm using kotlin version 2.2.10 in my project. I~'m not sure why it thinks I've "specified API version 2.0"~. Has anyone else run into this?

I recently updated datetime time from 0.6 to 0.7 But then it crashing at runtime in 3rd party libs that was build using older version on: "Failed resolution of: Lkotlinx/datetime/Instant" It means that there is no way how to migrate to that new version until all libraries will migrate? But nobody will migrate because nobody want to break somebody else project. I was expected that Kotlin is able to follow that alias even in runtime and use right class instead of kotlinx/datetime/Instant.