Java 8 – ZonedDateTime examples

Few Java 8 java.time.ZonedDateTime examples to show you how to convert a time zone between different countries.

1. Convert LocalDateTime to ZonedDateTime

The LocalDateTime has no time zone; to convert the LocalDateTime to ZonedDateTime, we can use .atZone(ZoneId.systemDefault()) to create a ZonedDateTime containing the system default time zone and convert it to another time zone using a predefined zone id or offset.

ZonedDateTimeExample1.java

package com.favtuts.time;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;

public class ZonedDateTimeExamples {

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

    static void convertLocalDateTimetoZonedDateTime() {
        LocalDateTime now = LocalDateTime.now();
        System.out.println(now);
        System.out.println("ZoneId.systemDefault(): " + ZoneId.systemDefault());

        // convert LocalDateTime to ZonedDateTime, with default system zone id
        ZonedDateTime zonedDateTime = now.atZone(ZoneId.systemDefault());

        // convert LocalDateTime to ZonedDateTime, with specified zoneId
        ZonedDateTime europeDateTime = zonedDateTime.withZoneSameInstant(ZoneId.of("Europe/Kaliningrad"));
        System.out.println(europeDateTime);

        // convert LocalDateTime to ZonedDateTime, with specified off set
        ZonedDateTime offSetNegative5 = now.atOffset(ZoneOffset.of("-05:00")).toZonedDateTime();
        System.out.println(offSetNegative5);

        // display all zone ids
        // ZoneId.getAvailableZoneIds().forEach(System.out::println);
    }
}

Output

2022-06-04T23:56:45.200739
ZoneId.systemDefault(): Asia/Ho_Chi_Minh
2022-06-04T18:56:45.200739+02:00[Europe/Kaliningrad]
2022-06-04T23:56:45.200739-05:00

2. Malaysia (UTC+08:00) -> Japan (UTC+09:00)

Review a flight detail from Malaysia Kuala Lumpur (UTC+08:00) to Japan Tokyo Haneda (UTC+09:00). The Japan Tokyo is one hour faster than Malaysia Kuala Lumpur.

Kuala Lumpur (KUL) -> Tokyo Haneda (HND)
Flight Duration : 7 hours

(KUL-Depart) 1430, 22 Aug 2016 ->  2230, 22 Aug 2016 (HND-Arrive)

The below program simulate the above flight detail if the flight is departing from Malaysia on 2016-08-22T14:30+08:00, and it will arrive in Tokyo around 2016-08-22T22:30+09:00, 7 hours flight duration.

ZonedDateTimeExample2.java

package com.favtuts.time;

import java.time.LocalDateTime;
import java.time.Month;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class ZonedDateTimeExamples {

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

    static void flightDetailFromMalaysiaToTokyo() {
        DateTimeFormatter format = DateTimeFormatter.ofPattern("HHmm, dd MMM uuuu");

        LocalDateTime ldt = LocalDateTime.of(2016, Month.AUGUST, 22, 14, 30);
        System.out.println("LocalDateTime : " + format.format(ldt));

        // UTC+8
        ZonedDateTime klDateTime = ldt.atZone(ZoneId.of("Asia/Kuala_Lumpur"));
        System.out.println("Depart : " + format.format(klDateTime));

        // UTC+9 and flight duration = 7 hours
        ZonedDateTime japanDateTime = klDateTime.withZoneSameInstant(ZoneId.of("Asia/Tokyo")).plusHours(7);
        System.out.println("Arrive : " + format.format(japanDateTime));

        System.out.println("\n---Detail---");
        System.out.println("Depart : " + klDateTime);
        System.out.println("Arrive : " + japanDateTime);
    }
}

Output

LocalDateTime : 1430, 22 Aug 2016
Depart : 1430, 22 Aug 2016
Arrive : 2230, 22 Aug 2016

---Detail---
Depart : 2016-08-22T14:30+08:00[Asia/Kuala_Lumpur]
Arrive : 2016-08-22T22:30+09:00[Asia/Tokyo]

3. France, Paris (UTC+02:00, DST) -> (UTC-05:00)

This time, a flight from France, Paris (UTC+02:00, DST) to a hardcoded ZoneOffset (UTC-05:00) time zone (e.g, New York).

France, Paris (FR) -> UTC-05:00
Flight Duration : 8 hours 10 minutes

(FR-Depart) 1430, 22 Aug 2016 ->  2230, 22 Aug 2016

ZonedDateTimeExample3.java

package com.favtuts.time;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class ZonedDateTimeExamples {

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

    static void flightDetailFromFranceParisToNewYork() {
        DateTimeFormatter format = DateTimeFormatter.ofPattern("HHmm, dd MMM uuuu");

        // Convert String to LocalDateTime
        String date = "2016-08-22 14:30";
        LocalDateTime ldt = LocalDateTime.parse(date, DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm"));
        System.out.println("LocalDateTime : " + format.format(ldt));

        // Paris, 2016 Apr-Oct = DST, UTC+2, other months UTC+1
        // UTC+2
        ZonedDateTime parisDateTime = ldt.atZone(ZoneId.of("Europe/Paris"));
        System.out.println("Depart : " + format.format(parisDateTime));

        // hard code a zoneoffset like this, UTC-5
        ZoneOffset nyOffSet = ZoneOffset.of("-05:00");
        ZonedDateTime nyDateTime = parisDateTime.withZoneSameInstant(nyOffSet).plusHours(8).plusMinutes(10);
        System.out.println("Arrive : " + format.format(nyDateTime));

        System.out.println("\n---Detail---");
        System.out.println("Depart : " + parisDateTime);
        System.out.println("Arrive : " + nyDateTime);
    }
}

Output

LocalDateTime : 1430, 22 Aug 2016
Depart : 1430, 22 Aug 2016
Arrive : 1540, 22 Aug 2016

---Detail---
Depart : 2016-08-22T14:30+02:00[Europe/Paris]
Arrive : 2016-08-22T15:40-05:00

Daylight Saving Time (DST)

Paris, normally UTC+1, has DST (add one hour = UTC+2) from 27/Mar to 30/Oct 2016. Review the above output, and the java.time.* APIs can calculate and handle the DST correctly.

Download Source Code

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

$ cd java-basic/time

References

• Daylight saving time
• ZonedDateTime JavaDoc
• Time Zone in Paris
• Java – Convert date and time between timezone
• Java 8 – Convert Instant to ZonedDateTime
• Java 8 – How to convert String to LocalDate
• How to compare dates in Java