Question

I’m converting a UTC time to another timezone, using this method:

SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date parsed = format.parse("2011-03-01 15:10:37");
TimeZone tz = TimeZone.getTimeZone("America/Chicago");
format.setTimeZone(tz);

String result = format.format(parsed);

So the input is 2011-03-01 15:10:37 but the output of this (value of result) is 2011-03-01 05:40:37. While it seems off, and according to this link, it should be 2011-03-01 09:10:37.

What am I doing wrong?

Answer 1

It turns out the code was almost correct, what I didn’t take into account was that when parsing the String to get a Date object initially, it uses default system TimeZone, so the source date was not in UTC as I expected.

The trick was to set the timezone when parsing the date to UTC and then set it to destination TimeZone. Something like this:

SimpleDateFormat sourceFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
sourceFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
Date parsed = sourceFormat.parse("2011-03-01 15:10:37"); // => Date is in UTC now

TimeZone tz = TimeZone.getTimeZone("America/Chicago");
SimpleDateFormat destFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
destFormat.setTimeZone(tz);

String result = destFormat.format(parsed);