KDateTime Multiplatform

A Kotlin Multiplatform library to provide regular date-time functionality needed with very minimal platform dependencies. It means upgrading OS / platform SDK target versions or moving to another platform would not break your application. Same and consistent core API set is provided to all JVM, Apple, JS targets.

Comparing with the kotlinx one, this library additionally provides formatting and parsing from custom formatted string. As it has extremely few dependencies, it is very lightweight. The sum of all the artifacts among all the platforms, including source jars and javadocs, is less than 700 KB.

This library is going to be stable. Tests are executed against every push in the mainstream, and the status can be seen at the top of this README. All major features have been implemented, but suggestions and contributions are welcomed!

This README is DEPRECATED

Read the documentation website instead. It is more organized and up-to-date.

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TL;DR

• APIs
• Examples
• Getting Started
• Limitations
• For Developers

Supported Platforms

• Android (Tested against compileSdk = 33, 34)
• Non-Android JVM (macOS tested against 14.0 beta, Java 17; Windows and Linux untested)
• JS (IR compiler only)
• iOS (Tested against 16.4)
• macOS Native (Tested against 14.0 beta)
• watchOS (Tested against 10.0 beta)
• tvOS (Tested against 17.0 beta)

APIs

Public classes / objects:

• KInstant (single point of time)
• KZonedInstant (single point of time + time zone offset)
• KZoneOffset (time zone offset)
• KZonedDateTime (date time + time zone offset)
• KDuration (a date-time length)
• KFixedTimeUnit (time unit)
• KDateTimeFormat (format and parse dates and times)
• KGregorianCalendar (conversion between timestamps and calendar dates)

Unlike Java, there is no local date or local datetime class here. That creates lots of usage issues. KZonedInstant or KZonedDateTime can be used instead.

There is also no time zone but time zone offset at this moment.

All of these classes are thread-safe, serializable and parcelable.

Supported custom format pattern symbols can be checked here. It has some difference with Java APIs.

Examples

Now, Time Zone Offset, Formatting, Calendar, Parsing

val now = KInstant.now()
println(now.toMilliseconds()) // 1694618242720

val localZoneOffset = KZoneOffset.local()
println(localZoneOffset.toDisplayString()) // +08:00

val localDateTime = now.atZoneOffset(localZoneOffset) // or now.atLocalZoneOffset()
println(localDateTime.format("yyyy-MM-dd'T'HH:mm:ss.lllZ")) // 2023-09-13T23:17:22.720+08:00
println(localDateTime.format("dd MMM yyyy h:mm:ss aa")) // 13 Sep 2023 11:17:22 pm

println(KZonedInstant.nowAtLocalZoneOffset()) // 2023-09-13T23:17:22.722+08:00

val japanDateTime = now.atZoneOffset(KZoneOffset(9, 0))
println(japanDateTime) // 2023-09-14T00:17:22.720+09:00
println(now at KZoneOffset(9, 0)) // 2023-09-14T00:17:22.720+09:00

val lastTrainTime = localDateTime.toKZonedDateTime().copy(hour = 23, minute = 10, second = 0, millisecond = 0)
println(KDateTimeFormat.ISO8601_DATETIME.format(lastTrainTime.toKZonedInstant())) // 2023-09-13T23:10:00+08:00

val parsedDateTime = KDateTimeFormat.ISO8601_DATETIME.parseToKZonedInstant("2023-09-10T17:18:53-07:00")
println(parsedDateTime.toMilliseconds()) // 1694391533000

val duration1 = 95.seconds()
println(duration1.format("m:ss")) // 1:35
println(duration1.format("m'm' s's'")) // 1m 35s

val dateTime = KInstant(1705677172000) // Friday, January 19, 2024 3:12:52 PM GMT
val formatter = KDateTimeFormat("E")
println(formatter.format(dateTime)) // Fri
formatter.weekDayNames = listOf("星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六")
println(formatter.format(dateTime)) // 星期五
println(dateTime.format("yyyy-MM-dd HH:mm:ss (z)")) // 2024-01-19 15:12:52 (+00:00)

Conversions

Time unit conversions.

val twoMinutes = 2.minutes()
println(twoMinutes.toSeconds()) // 120

Arithmetic, Comparison

val tomorrow = now + 1.days()
println(KDateTimeFormat.ISO8601_DATETIME.format(tomorrow)) // 2023-09-14T15:17:22Z

val duration2 = 1.minutes() + 35.seconds()
println(duration2.format("mm:ss")) // 01:35

println(tomorrow.atZoneOffset(KZoneOffset(-7, 0)) > now.atZoneOffset(KZoneOffset(8, 0))) // true

val oneDay = tomorrow - now
println(oneDay.toMilliseconds()) // 86400000

val sortedInstants = listOf(1694618242720, 1694618242723, 1694618242721, 1694618242722)
    .map { KInstant(it) }
    .sorted()
println(sortedInstants) // [2023-09-13T15:17:22.720Z, 2023-09-13T15:17:22.721Z, 2023-09-13T15:17:22.722Z, 2023-09-13T15:17:22.723Z]

val zonedDateTime = KZonedDateTime(
    year = 2023,
    month = 10,
    day = 4,
    hour = 13,
    minute = 8,
    second = 40,
    zoneOffset = KZoneOffset.parseFrom("+08:00")
)
val zonedDateTime2 = zonedDateTime + duration2
println(zonedDateTime2) // 2023-10-04T13:10:15.000+08:00

println(10_000.milliseconds() > 9.seconds()) // true

val closedTimeRange = KInstant(1709975163000) .. KInstant(1709975173000)
println(KZonedInstant(timestampMs = 1709975165000, zoneOffset = KZoneOffset(8, 0)) in closedTimeRange) // true

val openTimeRange = KZonedInstant(1709975163000, KZoneOffset(1, 0)) ..< KZonedInstant(1709975173000, KZoneOffset(1, 0))
println(KInstant(timestampMs = 1709975165000) in openTimeRange) // true

To use the in operator, manual importing an extension function is needed:

import com.sunnychung.lib.multiplatform.kdatetime.extension.contains

Serialization, Deserialization

This library supports kotlinx.serialization out of the box (except KDuration), to allow conversion between KDateTime classes and string from/to JSON, protobuf, etc.. Read examples here.

Besides, an additional type KInstantAsLong is provided for converting between timestamp in milliseconds (Long) and KInstant.

@Serializable
@AndroidParcelize
class TransitConnect : AndroidParcelable {
    lateinit var summary: Summary

    @Serializable
    @AndroidParcelize
    class Summary : WithDuration, AndroidParcelable {
        override lateinit var startAt: KZonedInstant
        override lateinit var endAt: KZonedInstant
        var walkingSeconds: Long = -1
        var waitingSeconds: Long = -1
        var numOfTrips: Int = -1
    }
}

Compatibility with platform-specific datetime APIs

From Kotlin side

iOS, JS, JVM

For example, for iOS targets:

val instant: KInstant = NSDate().toKInstant()
val date: NSDate = instant.toNSDate()

From native side

iOS

let instant: KInstant = KInstant.companion.now() as KInstant
let iosDate: Date = instant.toNSDate()
let instant2: KInstant = KDateTimeKt.KInstantFrom(date: iosDate)

For Android

The classes KInstant, KZonedInstant, KZonedDateTime, KZoneOffset, KDuration implement Parcelable.

Getting Started

First Step

Add the repository.

    repositories {
        mavenCentral()
    }

In the KMM / KMP application build.gradle.kts, include the dependency in the commonMain source set.

    sourceSets {
        val commonMain by getting {
            dependencies {
                api("io.github.sunny-chung:kdatetime-multiplatform:<version>")
                // ...
            }
        }
        // ...

After that, you can use KDateTime in any source set that depends on commonMain in Kotlin side.

To Use KDateTime in Swift / Objective-C

Add a transitive export to the framework DSL:

        framework {
            baseName = "shared"
            transitiveExport = true
            export("io.github.sunny-chung:kdatetime-multiplatform:<version>")
        }

In native side, import your common framework to use.

import shared

Limitations

• KDateTime does not deal with timezones. It deals with timezone offsets. There are no DST, calendar shifting, date skipping, leap seconds (but leap years are supported), etc..
• So, only datetimes from year 1753 onwards are supported
• Only timestamps between year 1753 and 3999 are supported
• Minimum time unit is millisecond
• English is default for locale-specific inputs and outputs (custom localized strings can be provided, check documentation)

For Developers

This section is only for developers who are interested in compiling or modifying this library.

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