Question about using a specific TimeZone to set a GregorianCalendar...

[Don Smith]

What I am trying to do is create a Gregorian calendar and set the time to
one second before Daylight Saving Time begins, and print it out. Then I
want to reset the time to 2:00 am and see if it realizes it is now in EDT.

Okay... so here's my sample code:

TimeZone tz = TimeZone.getTimeZone("Americas/New_York");
GregorianCalendar calendar = new GregorianCalendar(tz);
calendar.set(2009, 2, 8, 1, 59, 59);

System.out.println("Current date/time = " + calendar.getTime());

The output looks like the following:

Current date/time = Sat Mar 07 20:59:59 EST 2009

Clearly this is EST, which is good, but it's -5 hours back
from the time I wanted to set. Of cours if I substitute the
following line for the calendar.set line above:

calendar.set(2009, 2, 8, 6, 59, 59);

Then the output is:

Current date/time = Sun Mar 08 01:59:59 EST 2009

Of course I don't think I should have to do that.
I realize I am using the parent Calendar set()
method to do this, but shouldn't it use the same
TimeZone I set in the constructor? Do I have to
think in the GMT time, or is there a way to make
this set work as I imagined it?

Thanks,
DJ

[Paul Clapham]

You set the timezone of the Calendar object. So far so good. But then you extracted a Date object from that Calendar (via the getTime() method), and Date knows nothing of time zones. So already you've lost the time zone information. Then you print the Date; what time zone do you think it uses? It can't be the time zone belonging to the Calendar object, because the Date doesn't know or care what that was. No, it's your system's default time zone. Which presumably isn't Americas/New_York.

The way to fix that is to use a SimpleDateFormat object to format the Date for output. And to set its timezone to Americas/New_York.

[Don Smith]

That response definitely helped me find my mistake...

My default timezone is "America/New_York", NOT "Americas/New_York".

Once I used a valid time zone ID, it worked fine...

Thanks!