Java 8 – Convert Instant to ZonedDateTime

Java 8 examples to show you how to convert from Instant to ZonedDateTime

1. Instant -> ZonedDateTime

Example to convert a Instant UTC+0 to a Japan ZonedDateTime UTC+9

InstantZonedDateTime1.java

package com.favtuts.time;

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

public class InstantToZonedDateTime {
    
    public static void main(String[] args) {
        convertInstantToZonedDateTime();
    }

    static void convertInstantToZonedDateTime() {
        // Z = UTC+0
        Instant instant = Instant.now();

        System.out.println("Instant : " + instant);

        // Japan = UTC+9
        ZonedDateTime jpTime = instant.atZone(ZoneId.of("Asia/Tokyo"));

        System.out.println("ZonedDateTime JP: " + jpTime);

        System.out.println("OffSet JP: " + jpTime.getOffset());

        // Vietnam = UTC+7        
        ZonedDateTime vnTime = instant.atZone(ZoneId.of("Asia/Ho_Chi_Minh"));

        System.out.println("ZonedDateTime VN: " + vnTime);

        System.out.println("OffSet VN: " + vnTime.getOffset());

    }
}

Output

Instant : 2022-06-04T12:56:01.538799Z
ZonedDateTime JP: 2022-06-04T21:56:01.538799+09:00[Asia/Tokyo]
OffSet JP: +09:00
ZonedDateTime VN: 2022-06-04T19:56:01.538799+07:00[Asia/Ho_Chi_Minh]
OffSet VN: +07:00

2. ZonedDateTime -> Instant

Convert the Japan ZonedDateTime UTC+9 back to a Instant UTC+0/Z, review the result, the offset is taken care automatically.

InstantZonedDateTime2.java

package com.favtuts.time;

import java.time.*;

public class InstantToZonedDateTime {

    public static void main(String[] args) {
        convertZonedDateTimeToInstant();
    }

    static void convertZonedDateTimeToInstant() {
        LocalDateTime dateTime = LocalDateTime.of(2016, Month.AUGUST, 18, 6, 57, 38);

        // UTC+9
        ZonedDateTime jpTime = dateTime.atZone(ZoneId.of("Asia/Tokyo"));

        System.out.println("ZonedDateTime : " + jpTime);

        // Convert to instant UTC+0/Z , java.time helps to reduce 9 hours
        Instant instant = jpTime.toInstant();

        System.out.println("Instant : " + instant);
    }
}

Output

ZonedDateTime : 2016-08-18T06:57:38+09:00[Asia/Tokyo]
Instant : 2016-08-17T21:57:38Z

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/time

References

1. Wikipedia – ISO 8601 date format
2. Instant JavaDoc
3. ZoneddateTime JavaDoc