Is the HOUR in the Calendar class based on a specific time zone?

Question

I'm a little confused. I've been working with the Calendar and GregorianCalendar classes in Java and I have been printing the hour, but it says 4, and it is 11 where I am now.

My question is, is the hour based on the local time? Is it based on a specific time zone?

I've looked around, but I haven't found a clear answer.

    Calendar today = new GregorianCalendar();
    int y = today.get(Calendar.YEAR);
    int h = today.get(Calendar.HOUR);
    int ap = today.get(Calendar.AM_PM);
    System.out.println(y + " " + h + " " + ap);

And my output:

2013 4 1

Answer 1

The no-arg constructor of GregorianCalender uses Timzone.getDefault() as its timezone. This is the timezone (or in other words: the local time) of the JVM executing your code. All of the calendar fields, including Calendar.HOUR, are based on this timezone.

If this differs from your local time, then either the JVM is in a different timezone or the JVM (or rather its hosting computer) is configured incorrectly.