In joda time how to convert time zone without changing time

Question

I am getting UTC timestamp from database which is I am setting into a JodaTime DateTime instance

DateTime dt = new DateTime(timestamp.getTime())         


        

Answer 1

You can use the withZoneRetainFields() method of DateTime to alter the timezone without altering the numerals in the date.

Answer 2

If your timestamp is: 2015-01-01T00:00:00.000-0500 (this is local time [for me])

Try this:

DateTime localDt = new DateTime(timestamp.getTime())
    .withZoneRetainFields(DateTimeZone.UTC)
    .withZone(DateTimeZone.getDefault());

2014-12-31T19:00:00.000-05:00

Breaking it down: This gives you a DateTime corresponding to your timestamp, specifying that it is in UTC:

new DateTime(timestamp.getTime())
    .withZoneRetainFields(DateTimeZone.UTC)

2015-01-01T00:00:00.000Z

This gives you a DateTime but with the time converted to your local time:

new DateTime(timestamp.getTime())
    .withZoneRetainFields(DateTimeZone.UTC)
    .withZone(DateTimeZone.getDefault());

2014-12-31T19:00:00.000-05:00

Answer 3

Here's how I do it:

private DateTime convertLocalToUTC(DateTime eventDateTime) {

        // get your local timezone
        DateTimeZone localTZ = DateTimeZone.getDefault();

        // convert the input local datetime to utc  
        long eventMillsInUTCTimeZone = localTZ.convertLocalToUTC(eventDateTime.getMillis(), false);

        DateTime evenDateTimeInUTCTimeZone = new DateTime(eventMillsInUTCTimeZone);

        return evenDateTimeInUTCTimeZone.toDate();
}

Answer 4

I had the same problem. After reading this set of useful answers, and given my particular needs and available objects, I solved it by using another DateTime constructor:

new DateTime("2012-04-23T18:25:46.511Z", DateTimeZone.UTC)

Answer 5

You can use class LocalDateTime

LocalDateTime dt = new LocalDateTime(t.getTime()); 

and convert LocalDateTime to DateTime

DateTime dt = new LocalDateTime(timestamp.getTime()).toDateTime(DateTimeZone.UTC);  

Joda DateTime treats any time in millis like "millis since 1970y in current time zone". So, when you create DateTime instance, it is created with current time zone.

Answer 6

Also i have another approach that was very helpful for me. I wanted to have my workflow thread temporary changed to an specific Timezone (conserving the time), and then when my code finishes, i set the original timezone again. It turns out that when you are using joda libraries, doing:

TimeZone.setDefault(TimeZone.getTimeZone(myTempTimeZone));
TimeZone.setDefault(timeZone);

It's not enough. We also need to change the TimeZone in DateTimeZone as follows:

@Before
public void setUp() throws Exception {
    timeZone = TimeZone.getDefault();
    dateTimeZone = DateTimeZone.getDefault();
}

@After
public void tearDown() throws Exception {
    TimeZone.setDefault(timeZone);
    DateTimeZone.setDefault(dateTimeZone);
}

@Test
public void myTest() throws Exception {
    TimeZone.setDefault(TimeZone.getTimeZone(myTempTimeZone));
    DateTimeZone.setDefault(DateTimeZone.forID(myTempTimeZone));
    //TODO
    // my code with an specific timezone conserving time
}

Hope it helps to somebody else as well.