Working with Dates and Time in Kotlin: From A to Z — A Complete Guide

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Introduction to Working with Dates and Time in Kotlin

Working with dates and time is one of the most common tasks in modern development. Whether it's event logging, calculating deadlines, task scheduling, or displaying a user interface — proper handling of timestamps is essential. In Kotlin, which is fully compatible with Java, the de facto standard is the java.time package, introduced in Java 8. This package replaced the outdated java.util.Date and java.util.Calendar, offering a thread-safe, immutable, and intuitive API.

In this article, we will cover all key aspects of working with dates and time in Kotlin: from creating objects to formatting, parsing, and performing arithmetic operations. You will learn how to use LocalDate, LocalTime, LocalDateTime, Instant, Duration, and Period with practical examples.

1. Main Classes for Working with Dates and Time

The java.time package contains several key classes, each solving a specific task. Let's look at them in detail.

1.1 LocalDate — Working with Date Without Time

The LocalDate class represents a date (year, month, day) without time and time zone. It is ideal for birthdays, calendar events, and dates not tied to a specific moment.

import java.time.LocalDate

fun main() {    // Current date    val today = LocalDate.now()    println("Today: $today") // 2025-04-05

    // Specific date    val newYear = LocalDate.of(2025, 1, 1)    println("New Year: $newYear")

    // Parsing from string    val parsedDate = LocalDate.parse("2025-12-31")    println("Parsed date: $parsedDate")}

1.2 LocalTime — Working with Time Without Date

LocalTime stores only time (hours, minutes, seconds, nanoseconds). It is useful for storing the start time of a workday, schedules, or timers.

import java.time.LocalTime

fun main() {    // Current time    val now = LocalTime.now()    println("Now: $now")

    // Specific time    val meetingTime = LocalTime.of(14, 30, 0)    println("Meeting time: $meetingTime")

    // Parsing    val parsedTime = LocalTime.parse("09:15:30")    println("Parsed time: $parsedTime")}

1.3 LocalDateTime — Combining Date and Time

LocalDateTime combines LocalDate and LocalTime. This is the most commonly used class for storing a point in time without a time zone.

import java.time.LocalDateTime

fun main() {    // Current date and time    val current = LocalDateTime.now()    println("Now: $current")

    // Creating from components    val specific = LocalDateTime.of(2025, 4, 5, 10, 30, 0)    println("Specific moment: $specific")

    // Combining date and time    val date = LocalDate.of(2025, 12, 25)    val time = LocalTime.of(18, 0)    val christmas = LocalDateTime.of(date, time)    println("Christmas: $christmas")}

1.4 Instant — Point in Time in UTC

Instant represents a point on the timeline in Unix timestamp format (number of seconds and nanoseconds since January 1, 1970). It is indispensable for storing logs, working with databases, and exchanging data between systems.

import java.time.Instant

fun main() {    // Current moment in UTC    val now = Instant.now()    println("Now (UTC): $now")

    // From Unix timestamp    val fromEpoch = Instant.ofEpochSecond(1_700_000_000)    println("From timestamp: $fromEpoch")

    // Conversion to milliseconds    val millis = now.toEpochMilli()    println("Milliseconds: $millis")}