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androidtimejodatimeandroid-jodatime

Time zones - how to?

The final goal is to convert a timestamp passed down from the server to local time.

Here's what I get:

2018-04-05T16:14:19.130Z

However, my local time is 11:14 AM CST. Here's what I've tried: 

 final DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
 final LocalTime localTime = formatter.parseLocalTime(text);
 Timber.i(localTime.toString()); // output: 16:14:19.070

Output is: 16:14:19.070. Does anybody know how to use it? I expected to receive something like 11:14 AM.

Also, I've tried using this:

 final DateTimeFormatter formatter = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
 final DateTime time = formatter.parseDateTime(text);
 Timber.i(time.toString());  // output: 2018-04-05T16:14:19.490-05:00

Looks like it's a 5-hour difference there? Does anybody know how I can use this to convert to local time?

Solution

  • The "Z" in the end means that the date/time is in UTC. If you put it inside quotes, it's treated as a literal (the letter "Z" itself) and it loses this special meaning - you're basically throwing away the information that it's in UTC, and DateTime assumes the JVM default timezone (that's why your second attempt results in 16:14 in UTC-05:00).

    DateTime can parse this input directly:

    String input = "2018-04-05T16:14:19.130Z";
DateTime dt = DateTime.parse(input);

    Then you convert this to the desired timezone. You can do:

    dt = dt.withZone(DateTimeZone.getDefault());

    Which will use your JVM's default timezone. But this is not so reliable, because the default can be changed at runtime - even by other applications running in the same JVM - so it's better to use an explicit timezone:

    dt = dt.withZone(DateTimeZone.forID("America/Chicago"));

    Then you can convert it to the format you want:

    String time = dt.toString("hh:mm a"); // 11:14 AM

    If you need to use a formatter, you can remove the quotes around "Z" and also set the timezone in the formatter:

    DateTimeFormatter parser = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ")
    // zone to be used for the formatter
    .withZone(DateTimeZone.forID("America/Chicago"));
DateTime dateTime = parser.parseDateTime("2018-04-05T16:14:19.130Z");
String time = dateTime.toString("hh:mm a"); // 11:14 AM