When I execute this code in plain java and in android, I get different results:

System.out.println(new Date(1311940549187l).toString());

• In plain java, I get this output: Fri Jul 29 13:55:49 CEST 2011

• In android, I get this output: Fri Jul 29 11:55:49 GMT+00:00 2011

I understand it has something to do with the time zone. But I really need to get the same output. How can I generate a Date object based on a Long value, and开发者_如何学编程 get the same date in both environments ?

Edit: I already use SimpleDateFormat and the two datetimes have 2 hours offset. Please tell me how to get rid of the offset.

this is how I use the SimpleDateFormat: new SimpleDateFormat("MM-dd-yyyy HH:mm")

The date is the same in both environment, but toString() gives a different result because the two environments are configured with a different timezone.

To format a date for a specific timezone, use a SimpleDateFormat and set the timezone to a specific value (GMT for instance).

UPDATE:

TimeZone gmt = TimeZone.getTimeZone("GMT");
SimpleDateFormat format = new SimpleDateFormat("...");
format.setCalendar(Calendar.getInstance(gmt));

You could use a SimpleDateFormat and convert the java code to match the output of what android is giving you.

SimpleDateFormat

Or Vice versa (Android convert to match java)

Android SimpleDateFormat

dFormat = new SimpleDateFormat("MM-dd-yyyy HH:mm")
TimeZone tz = TimeZone.getTimeZone("GMT:00"); 
dFormat .setTimeZone( tz );

tl;dr

Instant
.ofEpochMilli( 1_311_940_549_187L )
.toString()

2011-07-29T11:55:49.187Z

java.time

The modern solution uses java.time classes. The terrible java.util.Date class was replaced by java.time.Instant. Both represent a moment as seen in UTC. The Instant class is much better behaved in that it does not inject time zones in unexpected ways like Date does. Never use java.util.Date.

Parse your count of milliseconds since epoch reference of first moment of 1970 in UTC as a java.time.Instant object.

Instant instant = Instant.ofEpochMilli( 1_311_940_549_187L ) ;

Generate text in standard ISO 8601 format.

String output = instant.toString() ;

2011-07-29T11:55:49.187Z

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. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
  • Java 9 brought some minor features and fixes.
• Java SE 6 and Java SE 7
  • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android (26+) bundle implementations of the java.time classes.
  • For earlier Android (<26), a process known as API desugaring brings a subset of the java.time functionality not originally built into Android.
    • If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….