Force Java timezone as GMT/UTC

106
votes

I need to force any time related operations to GMT/UTC, regardless the timezone set on the machine. Any convenient way to so in code?

To clarify, I'm using the DB server time for all operations, but it comes out formatted according to local timezone.

Thanks!

13
javatimezoneutcgmt
Actually, his problem is a subset of mine, but I found a solution. – SyBer
Look at the duplicate question, and search for "Joda" and "DateTimeZone". – Basil Bourque

13 Answers

131
votes

The OP answered this question to change the default timezone for a single instance of a running JVM, set the user.timezone system property:

java -Duser.timezone=GMT ... <main-class>

If you need to set specific time zones when retrieving Date/Time/Timestamp objects from a database ResultSet, use the second form of the getXXX methods that takes a Calendar object:

Calendar tzCal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
ResultSet rs = ...;
while (rs.next()) {
    Date dateValue = rs.getDate("DateColumn", tzCal);
    // Other fields and calculations
}

Or, setting the date in a PreparedStatement:

Calendar tzCal = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
PreparedStatement ps = conn.createPreparedStatement("update ...");
ps.setDate("DateColumn", dateValue, tzCal);
// Other assignments
ps.executeUpdate();

These will ensure that the value stored in the database is consistent when the database column does not keep timezone information.

The java.util.Date and java.sql.Date classes store the actual time (milliseconds) in UTC. To format these on output to another timezone, use SimpleDateFormat. You can also associate a timezone with the value using a Calendar object:

TimeZone tz = TimeZone.getTimeZone("<local-time-zone>");
//...
Date dateValue = rs.getDate("DateColumn");
Calendar calValue = Calendar.getInstance(tz);
calValue.setTime(dateValue);

Usefull Reference

https://docs.oracle.com/javase/9/troubleshoot/time-zone-settings-jre.htm#JSTGD377

https://confluence.atlassian.com/kb/setting-the-timezone-for-the-java-environment-841187402.html

24
votes

Also if you can set JVM timezone this way

System.setProperty("user.timezone", "EST");

or -Duser.timezone=GMT in the JVM args.

13
votes

I had to set the JVM timezone for Windows 2003 Server because it always returned GMT for new Date();

-Duser.timezone=America/Los_Angeles

Or your appropriate time zone. Finding a list of time zones proved to be a bit challenging also...

Here are two list;

http://wrapper.tanukisoftware.com/doc/english/prop-timezone.html

http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=%2Frzatz%2F51%2Fadmin%2Freftz.htm

12
votes

You could change the timezone using TimeZone.setDefault():

TimeZone.setDefault(TimeZone.getTimeZone("GMT"))
8
votes

for me, just quick SimpleDateFormat, 

  private static final SimpleDateFormat GMT = new SimpleDateFormat("yyyy-MM-dd");
  private static final SimpleDateFormat SYD = new SimpleDateFormat("yyyy-MM-dd");
  static {
      GMT.setTimeZone(TimeZone.getTimeZone("GMT"));
    SYD.setTimeZone(TimeZone.getTimeZone("Australia/Sydney"));
  }

then format the date with different timezone.

8
votes

tl;dr

String sql = "SELECT CURRENT_TIMESTAMP ;
…
OffsetDateTime odt = myResultSet.getObject( 1 , OffsetDateTime.class ) ;

Avoid depending on host OS or JVM for default time zone

I recommend you write all your code to explicitly state the desired/expected time zone. You need not depend on the JVM’s current default time zone. And be aware that the JVM’s current default time zone can change at any moment during runtime, with any code in any thread of any app calling TimeZone.setDefault. Such a call affects all apps within that JVM immediately.

java.time

Some of the other Answers were correct, but are now outmoded. The terrible date-time classes bundled with the earliest versions of Java were flawed, written by people who did not understand the complexities and subtleties of date-time handling.

The legacy date-time classes have been supplanted by the java.time classes defined in JSR 310.

To represent a time zone, use ZoneId. To represent an offset-from-UTC, use ZoneOffset. An offset is merely a number of hour-minutes-seconds ahead or behind the prime meridian. A time zone is much more. A time zone is a history of the past, present, and future changes to the offset used by the people of a particular region.

I need to force any time related operations to GMT/UTC

For an offset of zero hours-minutes-seconds, use the constant ZoneOffset.UTC.

Instant

To capture the current moment in UTC, use an Instant. This class represent a moment in UTC, always in UTC by definition.

Instant instant = Instant.now() ;  // Capture current moment in UTC.

ZonedDateTime

To see that same moment through the wall-clock time used by the people of a particular region, adjust into a time zone. Same moment, same point on the timeline, different wall-clock time.

ZoneId z = ZoneId.of( "Asia/Tokyo" ) ;
ZonedDateTime zdt = instant.atZone( z ) ;

Database

You mention a database.

To retrieve a moment from the database, your column should be of a data type akin to the SQL-standard TIMESTAMP WITH TIME ZONE. Retrieve an object rather than a string. In JDBC 4.2 and later, we can exchange java.time objects with the database. The OffsetDateTime is required by JDBC, while Instant & ZonedDateTime are optional. 

OffsetDateTime odt = myResultSet.getObject( … , OffsetDateTime.class ) ;

In most databases and drivers, I would guess that you will get the moment as seen in UTC. But if not, you can adjust in either of two ways:

  • Extract a Instant: odt.toInstant()
  • Adjust from the given offset to an offset of zero: OffsetDateTime odtUtc = odt.withOffsetSameInstant( ZoneOffset.UTC ) ;`.

Table of date-time types in Java (both legacy and modern) and in standard SQL

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

6
votes

I would retrieve the time from the DB in a raw form (long timestamp or java's Date), and then use SimpleDateFormat to format it, or Calendar to manipulate it. In both cases you should set the timezone of the objects before using it.

See SimpleDateFormat.setTimeZone(..) and Calendar.setTimeZone(..) for details

3
votes

Use system property:

-Duser.timezone=UTC
1
votes

create a pair of client / server, so that after the execution, client server sends the correct time and date. Then, the client asks the server pm GMT and the server sends back the answer right.

1
votes

Execute this line in MySQL to reset your timezone:

SET @@global.time_zone = '+00:00';
0
votes

Hope below code will help you.

    DateFormat formatDate = new SimpleDateFormat(ISO_DATE_TIME_PATTERN);
    formatDate.setTimeZone(TimeZone.getTimeZone("UTC")); 
    formatDate.parse(dateString);
-1
votes

Wow. I know this is an ancient thread but all I can say is do not call TimeZone.setDefault() in any user-level code. This always sets the Timezone for the whole JVM and is nearly always a very bad idea. Learn to use the joda.time library or the new DateTime class in Java 8 which is very similar to the joda.time library.

-6
votes

If you would like to get GMT time only with intiger: var currentTime = new Date(); var currentYear ='2010' var currentMonth = 10; var currentDay ='30' var currentHours ='20' var currentMinutes ='20' var currentSeconds ='00' var currentMilliseconds ='00'

currentTime.setFullYear(currentYear);
currentTime.setMonth((currentMonth-1)); //0is January
currentTime.setDate(currentDay);  
currentTime.setHours(currentHours);
currentTime.setMinutes(currentMinutes);
currentTime.setSeconds(currentSeconds);
currentTime.setMilliseconds(currentMilliseconds);

var currentTimezone = currentTime.getTimezoneOffset();
currentTimezone = (currentTimezone/60) * -1;
var gmt ="";
if (currentTimezone !== 0) {
  gmt += currentTimezone > 0 ? ' +' : ' ';
  gmt += currentTimezone;
}
alert(gmt)