Question

I’m trying to use JODA to simply convert a numeric timestamp (a long representing Unix epoch time), to a Month Day, Year string.

Here’s code I just ran a few seconds ago:

    long lTimestamp = 1315600867;  // Current timestamp is approx 9/9/11 3:41 PM EST

    DateTime oTimestamp = new DateTime(lTimestamp);
    String strMon, strDay, strYear;
    strMon = oTimestamp.monthOfYear().getAsText(Locale.ENGLISH);
    strDay = oTimestamp.dayOfMonth().getAsText(Locale.ENGLISH);
    strYear = oTimestamp.year().getAsText(Locale.ENGLISH);

    String strDate = strMon + " " + strDay + ", " + strYear;

    System.out.println("Converted timestamp is : " + strDate);

The output to this is January 16, 1970!!!

Does this make any sense to anyone?!?!

Answer 1

The long you pass into the DateTime constructor is meant to be in milliseconds, not seconds – so use 1315600867000L instead and it’s all fine.

Documentation states:

Constructs an instance set to the milliseconds from 1970-01-01T00:00:00Z using ISOChronology in the default time zone.

If you’re getting a value which is already in seconds, you just need to multiply by 1000:

long timestampInSeconds = getValueFromDatabase();
long timestampInMillis = timestampInSeconds * 1000L;
DateTime dt = new DateTime(timestampInMillis);

I’d actually advise you to use Instant in this case rather than DateTime – you don’t really have a time zone to consider. If you are going to use DateTime, you should specify the time zone explicitly, e.g.

DateTime dt = new DateTime(timestampInMillis, DateTimeZone.UTC);