Output RFC 3339 Timestamp in Java

Starting in Java 7, there’s the X pattern string for ISO8601 time zone. For strings in the format you describe, use XXX. See the documentation.

Sample:

System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX")
        .format(new Date()));

Result:

2014-03-31T14:11:29+02:00