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Java – Convert date and time between timezone

ByFavTuts Editorial

Jun 4, 2022 #calendar, #date, #java, #joda-time, #time, #timezone, #zoneddatetime

In this tutorial, we will show you few examples (ZonedDateTime (Java 8), Date, Calendar and Joda Time) to convert a date and time between different time zones.

All examples will be converting the date and time from

(UTC+8:00) Asia/Singapore - Singapore Time
Date : 22-1-2015 10:15:55 AM

to

(UTC-5:00) America/New_York - Eastern Standard Time
Date : 21-1-2015 09:15:55 PM

Which to use?
For time zone, avoid both Date and Calendar

1 – If you are using JDK >= 8, use the new java.time.* framework.

2 – If you are using JDK < 8, use Joda Time. (The new Java 8 java.time.* framework is inspired by this library)

1. ZonedDateTime

Always use this new Java 8 java.time.ZonedDateTime to represent a date and time containing time zone.

ZonedDateTimeExample.java

package com.favtuts.time;

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

public class BetweenTimeZone {

    private static final String DATE_FORMAT = "dd-M-yyyy hh:mm:ss a";

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

    static void switchTimeZoneWithZonedDateTime() {
        // Always use this new Java 8 java.time.ZonedDateTime

        String dateInString = "22-1-2015 10:15:55 AM";
        LocalDateTime ldt = LocalDateTime.parse(dateInString, DateTimeFormatter.ofPattern(DATE_FORMAT));

        ZoneId singaporeZoneId = ZoneId.of("Asia/Singapore");
        System.out.println("TimeZone : " + singaporeZoneId);

        //LocalDateTime + ZoneId = ZonedDateTime
        ZonedDateTime asiaZonedDateTime = ldt.atZone(singaporeZoneId);
        System.out.println("Date (Singapore) : " + asiaZonedDateTime);

        ZoneId newYokZoneId = ZoneId.of("America/New_York");
        System.out.println("TimeZone : " + newYokZoneId);

        ZonedDateTime nyDateTime = asiaZonedDateTime.withZoneSameInstant(newYokZoneId);
        System.out.println("Date (New York) : " + nyDateTime);

        DateTimeFormatter format = DateTimeFormatter.ofPattern(DATE_FORMAT);
        System.out.println("\n---DateTimeFormatter---");
        System.out.println("Date (Singapore) : " + format.format(asiaZonedDateTime));
        System.out.println("Date (New York) : " + format.format(nyDateTime));
    }
}

Output

TimeZone : Asia/Singapore
Date (Singapore) : 2015-01-22T10:15:55+08:00[Asia/Singapore]
TimeZone : America/New_York
Date (New York) : 2015-01-21T21:15:55-05:00[America/New_York]

---DateTimeFormatter---
Date (Singapore) : 22-1-2015 10:15:55 AM
Date (New York) : 21-1-2015 09:15:55 PM

Note

Refer to this ZonedDateTime tutorial for more time zone, custom offset and daylight saving time (DST) examples.

2. Date

Note
The java.util.Date has no concept of time zone, and only represents the number of seconds passed since the Unix epoch time – 1970-01-01T00:00:00Z. But, if you print the Date object directly, the Date object will be always printed with the default system time zone. Check the Date.toString() source code.

2.1 Set a time zone to DateFormat and format the java.util.Date

SimpleDateFormat sdfAmerica = new SimpleDateFormat("dd-M-yyyy hh:mm:ss a");
sdfAmerica.setTimeZone(TimeZone.getTimeZone("America/New_York"));
String sDateInAmerica = sdfAmerica.format(date);

2.2 Full example

DateExample.java

package com.favtuts.time;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

public class BetweenTimeZone {

    private static final String DATE_FORMAT = "dd-M-yyyy hh:mm:ss a";

    public static void main(String[] args) throws ParseException {
        switchTimeZoneWithClassicDate();
    }

    static void switchTimeZoneWithClassicDate() throws ParseException {
        SimpleDateFormat formatter = new SimpleDateFormat(DATE_FORMAT);

        String dateInString = "22-01-2015 10:15:55 AM";
        Date date = formatter.parse(dateInString);
        TimeZone tz = TimeZone.getDefault();

        // From TimeZone Asia/Singapore
        System.out.println("TimeZone : " + tz.getID() + " - " + tz.getDisplayName());
        System.out.println("TimeZone : " + tz);
        System.out.println("Date (Singapore) : " + formatter.format(date));

        // To TimeZone America/New_York
        SimpleDateFormat sdfAmerica = new SimpleDateFormat(DATE_FORMAT);
        TimeZone tzInAmerica = TimeZone.getTimeZone("America/New_York");
        sdfAmerica.setTimeZone(tzInAmerica);

        String sDateInAmerica = sdfAmerica.format(date); // Convert to String first
        Date dateInAmerica = formatter.parse(sDateInAmerica); // Create a new Date object

        System.out.println("\nTimeZone : " + tzInAmerica.getID() + " - " + tzInAmerica.getDisplayName());
        System.out.println("TimeZone : " + tzInAmerica);
        System.out.println("Date (New York) (String) : " + sDateInAmerica);
        System.out.println("Date (New York) (Object) : " + formatter.format(dateInAmerica));
    }
}

Output

TimeZone : Asia/Ho_Chi_Minh - Indochina Time
TimeZone : sun.util.calendar.ZoneInfo[id="Asia/Ho_Chi_Minh",...]
Date (Singapore) : 22-1-2015 10:15:55 AM

TimeZone : America/New_York - Eastern Standard Time
TimeZone : sun.util.calendar.ZoneInfo[id="America/New_York",...]
Date (New York) (String) : 21-1-2015 10:15:55 PM
Date (New York) (Object) : 21-1-2015 10:15:55 PM

3. Calendar

3.1 A Calendar example to set a time zone :

	Calendar calendar = new GregorianCalendar();
	calendar.setTime(date);
	calendar.setTimeZone(tzInAmerica);

A super common mistake is to get the java.util.Date directly like this :

	//Wrong, it will display 22-1-2015 10:15:55 AM, time is still in the system default time zone!
	Date dateInAmerican = calendar.getTime());

In the above example, no matter what time zone you set in the Calendar, the Date object will be always printed with the default system time zone. (Check the Date.toString() source code)

3.2 The correct way should be using the DateFormat to format it :

	SimpleDateFormat sdfAmerica = new SimpleDateFormat("dd-M-yyyy hh:mm:ss a");
	TimeZone tzInAmerica = TimeZone.getTimeZone("America/New_York");
	sdfAmerica.setTimeZone(tzInAmerica);
	sdfAmerica.format(calendar.getTime())

or get the Date via calendar.get() :

	int year = calendar.get(Calendar.YEAR);
	int month = calendar.get(Calendar.MONTH); // Jan = 0, dec = 11
	int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
	int hour = calendar.get(Calendar.HOUR); // 12 hour clock
	int hourOfDay = calendar.get(Calendar.HOUR_OF_DAY); // 24 hour clock
	int minute = calendar.get(Calendar.MINUTE);
	int second = calendar.get(Calendar.SECOND);
	int ampm = calendar.get(Calendar.AM_PM); //0 = AM , 1 = PM

3.3 Full example

CalendarExample.java

package com.favtuts.time;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone;

public class BetweenTimeZone {

    private static final String DATE_FORMAT = "dd-M-yyyy hh:mm:ss a";

    public static void main(String[] args) throws ParseException {
        switchTimeZoneWithCalendar();
    }

    static void switchTimeZoneWithCalendar() throws ParseException {
        SimpleDateFormat formatter = new SimpleDateFormat(DATE_FORMAT);

        String dateInString = "22-01-2015 10:15:55 AM";
        Date date = formatter.parse(dateInString);
        TimeZone tz = TimeZone.getDefault();

        // From TimeZone Asia/Singapore
        System.out.println("TimeZone : " + tz.getID() + " - " + tz.getDisplayName());
        System.out.println("TimeZone : " + tz);
        System.out.println("Date (Singapore) : " + formatter.format(date));

        // To TimeZone America/New_York
        SimpleDateFormat sdfAmerica = new SimpleDateFormat(DATE_FORMAT);
        TimeZone tzInAmerica = TimeZone.getTimeZone("America/New_York");
        sdfAmerica.setTimeZone(tzInAmerica);

        Calendar calendar = new GregorianCalendar();
        calendar.setTime(date);
        calendar.setTimeZone(tzInAmerica);

        System.out.println("\nTimeZone : " + tzInAmerica.getID() + " - " + tzInAmerica.getDisplayName());
        System.out.println("TimeZone : " + tzInAmerica);

        //Wrong! It will print the date with the system default time zone
        System.out.println("Date (New York) (Wrong!): " + calendar.getTime());

        //Correct! need formatter
        System.out.println("Date (New York) (Correct!) : " + sdfAmerica.format(calendar.getTime()));

        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH); // Jan = 0, dec = 11
        int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH);
        int hour = calendar.get(Calendar.HOUR); // 12 hour clock
        int hourOfDay = calendar.get(Calendar.HOUR_OF_DAY); // 24 hour clock
        int minute = calendar.get(Calendar.MINUTE);
        int second = calendar.get(Calendar.SECOND);
        int ampm = calendar.get(Calendar.AM_PM); //0 = AM , 1 = PM

        //Correct
        System.out.println("\nyear \t\t: " + year);
        System.out.println("month \t\t: " + month + 1);
        System.out.println("dayOfMonth \t: " + dayOfMonth);
        System.out.println("hour \t\t: " + hour);
        System.out.println("minute \t\t: " + minute);
        System.out.println("second \t\t: " + second);
        System.out.println("ampm \t\t: " + ampm);
    }
}

Output

TimeZone : Asia/Ho_Chi_Minh - Indochina Time
TimeZone : sun.util.calendar.ZoneInfo[id="Asia/Ho_Chi_Minh",...]
Date (Singapore) : 22-1-2015 10:15:55 AM

TimeZone : America/New_York - Eastern Standard Time
TimeZone : sun.util.calendar.ZoneInfo[id="America/New_York",...]
Date (New York) (Wrong!): Thu Jan 22 10:15:55 ICT 2015
Date (New York) (Correct!) : 21-1-2015 10:15:55 PM

year            : 2015
month           : 01
dayOfMonth      : 21
hour            : 10
minute          : 15
second          : 55
ampm            : 1

4. Joda Time

4.1 A Joda Time example to set a time zone :

	DateTime dt = new DateTime(date);
	DateTimeZone dtZone = DateTimeZone.forID("America/New_York");
	DateTime dtus = dt.withZone(dtZone);

Again, a common mistake is getting the Date directly like this, time zone will be lost.

	//Output : 22-1-2015 10:15:55 AM
	Date dateInAmerica = dtus.toDate();

The correct way is converted to Joda LocalDateTime first.

	//Output : 21-1-2015 09:15:55 PM
	Date dateInAmerica = dtus.toLocalDateTime().toDate();

4.2 Full example

pom.xml

<!-- https://mvnrepository.com/artifact/joda-time/joda-time -->
<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.10.14</version>
</dependency>

JodaTimeExample.java

package com.favtuts.time;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;

public class BetweenTimeZone {

    private static final String DATE_FORMAT = "dd-M-yyyy hh:mm:ss a";

    public static void main(String[] args) throws ParseException {
        switchTimeZoneWithJodaTime();
    }

    static void switchTimeZoneWithJodaTime() throws ParseException {
        SimpleDateFormat formatter = new SimpleDateFormat(DATE_FORMAT);

        String dateInString = "22-01-2015 10:15:55 AM";
        Date date = formatter.parse(dateInString);
        TimeZone tz = TimeZone.getDefault();

        // From TimeZone Asia/Singapore
        System.out.println("TimeZone : " + tz.getID() + " - " + tz.getDisplayName());
        System.out.println("TimeZone : " + tz);
        System.out.println("Date (Singapore) : " + formatter.format(date));

        // To TimeZone America/New_York
        SimpleDateFormat sdfAmerica = new SimpleDateFormat(DATE_FORMAT);
        DateTime dt = new DateTime(date);
        DateTimeZone dtZone = DateTimeZone.forID("America/New_York");
        DateTime dtus = dt.withZone(dtZone);
        TimeZone tzInAmerica = dtZone.toTimeZone();
        Date dateInAmerica = dtus.toLocalDateTime().toDate(); //Convert to LocalDateTime first

        sdfAmerica.setTimeZone(tzInAmerica);
        System.out.println("\nTimeZone : " + tzInAmerica.getID() + " - " + tzInAmerica.getDisplayName());
        System.out.println("TimeZone : " + tzInAmerica);
        System.out.println("DateTimeZone : " + dtZone);
        System.out.println("DateTime : " + dtus);

        System.out.println("dateInAmerica (Formatter) : " + formatter.format(dateInAmerica));
        System.out.println("dateInAmerica (Object) : " + dateInAmerica);
    }
}

Output

TimeZone : Asia/Ho_Chi_Minh - Indochina Time
TimeZone : sun.util.calendar.ZoneInfo[id="Asia/Ho_Chi_Minh",...]
Date (Singapore) : 22-1-2015 10:15:55 AM

TimeZone : America/New_York - Eastern Standard Time
TimeZone : sun.util.calendar.ZoneInfo[id="America/New_York",...]
DateTimeZone : America/New_York
DateTime : 2015-01-21T22:15:55.000-05:00
dateInAmerica (Formatter) : 21-1-2015 10:15:55 PM
dateInAmerica (Object) : Wed Jan 21 22:15:55 ICT 2015

P.S Tested with Joda-time 2.10.14

Download Source Code

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

$ cd java-basic/time

References

  1. Date and Time Manipulation in Java Using JodaTime
  2. World Time Server
  3. Java 8 – ZonedDateTime examples
  4. Java 8 – Convert Date to LocalDate and LocalDateTime
  5. ZonedDateTime Javadoc
  6. Calendar JavaDoc
  7. Date JavaDoc
  8. SimpledateFormat JavaDoc

By FavTuts Editorial

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