Convert IST to PST in java

Question

Hi I have a date/Time field i want to get Convert current IST to CURRENT PST in java... need help....

ex: now in IST its :13/may/2011 3.32.58pm want the same in PST i.e. 13/may/2011 3.02.58 AM

thank you........

Answer 1

If you're interested in the current time, you don't need to know about IST at all... just the current instance, and the conversion to PST. You can do this with something like:

Date now = new Date();
TimeZone zone = TimeZone.getTimeZone("America/Los_Angeles"); // For example...
DateFormat format = new SimpleDateFormat("..."); // Put your pattern here
format.setTimeZone(zone);
String text = format.format(now);

Personally I'd recommend you use Joda Time for all date/time work instead, as it's a much nicer API - but in this case it's really pretty simple even with the built-in API.

Answer 2

The Answer by Jon Skeet is correct but now outdated with the arrival of the java.time code in Java 8 and later.

java.time

The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).

Get current moment in UTC.

Instant instant = Instant.now();

Adjust into a time zone.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Los_Angeles" );
ZonedDateTime zdt = instant.atZone( z );

To generate a String in standard ISO 8601 format, call the toString. For alternate formatting, use the DateTimeFormatter class already covered in many other Questions and Answers.

String output = zdt.format( myDateTimeFormatter );

See the same moment in India time, specifically Asia/Kolkata.

ZoneId zKolkata = ZoneId.of( "Asia/Kolkata" );
ZonedDateTime zdtKolkata = zdt.withZoneSameInstant( zKolkata );

I am not sure if by IST you meant India Standard Time or Irish Standard Time. Let's cover Europe/Dublin as well. That zone happens to currently use an offset of zero, +00:00. So its wall-clock time in the same as UTC.

ZoneId zDublin = ZoneId.of( "Europe/Dublin" );
ZonedDateTime zdtDublin = zdt.withZoneSameInstant( zDublin );

See this code run live at IdeOne.com.

instant.toString(): 2017-02-13T07:28:57.738Z

zdt.toString(): 2017-02-12T23:28:57.738-08:00[America/Los_Angeles]

zdtKolkata.toString(): 2017-02-13T12:58:57.738+05:30[Asia/Kolkata]

zdtDublin.toString(): 2017-02-13T07:28:57.738Z[Europe/Dublin]

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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.

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

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

Where to obtain the java.time classes?

• Java SE 8 and SE 9 and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.