Get GMT Time in Java

Odds are good you did the right stuff on the back end in getting the date, but there's nothing to indicate that you didn't take that GMT time and format it according to your machine's current locale.

final Date currentTime = new Date();

final SimpleDateFormat sdf =
        new SimpleDateFormat("EEE, MMM d, yyyy hh:mm:ss a z");

// Give it to me in GMT time.
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
System.out.println("GMT time: " + sdf.format(currentTime));

The key is to use your own DateFormat, not the system provided one. That way you can set the DateFormat's timezone to what you wish, instead of it being set to the Locale's timezone.

I wonder why no one does this:

Calendar time = Calendar.getInstance();
time.add(Calendar.MILLISECOND, -time.getTimeZone().getOffset(time.getTimeInMillis()));
Date date = time.getTime();

Update: Since Java 8,9,10 and more, there should be better alternatives supported by Java. Thanks for your comment @humanity

From my experience, the bundled Calendar and Date classes in Java can yield undersired effect. If you wouldn't mind upgrading to Java 8, then consider using ZonedDateTime

like so:

ZonedDateTime currentDate = ZonedDateTime.now( ZoneOffset.UTC );

tl;dr

Instant.now()

java.time

The Answer by Damilola is correct in suggesting you use the java.time framework built into Java 8 and later. But that Answer uses the ZonedDateTime class which is overkill if you just want UTC rather than any particular time zone.

The troublesome old date-time classes are now legacy, supplanted by the java.time classes.

Instant

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).

Simple code:

Instant instant = Instant.now() ;

instant.toString(): 2016-11-29T23:18:14.604Z

You can think of Instant as the building block to which you can add a time zone (ZoneID) to get a ZonedDateTime.

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

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 java.time.

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….

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.

To get the time in millis at GMT all you need is

long millis = System.currentTimeMillis();

You can also do

long millis = new Date().getTime();

and

long millis = 
    Calendar.getInstance(TimeZone.getTimeZone("GMT")).getTimeInMillis();

but these are inefficient ways of making the same call.