Instant and ZonedDateTime

Learn time zones with Instant and ZonedDateTime.

Instant and ZonedDateTime

Instant represents a single point on the timeline in UTC. ZonedDateTime adds zone information; this lets the same moment be shown in different regions' local times.

Example: Instant now = Instant.now(). This gives the current moment in UTC. With ZonedDateTime zdt = now.atZone(ZoneId.of("Europe/Istanbul")) the moment is converted to Istanbul time. Instant is suited for storing timestamps; ZonedDateTime is for regional display.

Converting Instant and ZonedDateTime

To turn an Instant into a regional time you use atZone. The reverse is toInstant. These conversions handle time math in global systems.

Example: zdt.toInstant() turns any regional time back to UTC. This lets you compare two regions' times: first convert both to Instant, then take the difference. Since the zone information is gone, the result is always precise and comparable.

Exercise Print the year with ZonedDateTime

Create a zoned datetime with ZonedDateTime.of(2024, 1, 15, 10, 30, 0, 0, ZoneId.of("UTC")). Print the year with getYear() via System.out.println.

Show example solution

import java.time.ZonedDateTime;
import java.time.ZoneId;

public class ZoneExample {
    public static void main(String[] args) {
        ZonedDateTime zdt = ZonedDateTime.of(2024, 1, 15, 10, 30, 0, 0, ZoneId.of("UTC"));
        System.out.println(zdt.getYear());
    }
}

Test yourself

Match the time classes

Instant

UTC time point
ZonedDateTime

Time with zone
Instant.now

Current UTC
ZoneId

Zone identifier
Which class represents a single UTC point in time?
- LocalDate
- Period
- Instant
- LocalTime
Show answer

Instant — Instant is a UTC point in time.

Complete the atZone call

ZonedDateTime zdt = instant.____(ZoneId.of("UTC"));

Show answer

ZonedDateTime zdt = instant.atZone(ZoneId.of("UTC"));

Next lesson: Summary - Date/time API

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