Java: SimpleDateFormat adds 1 to day and hour (Time span)

Question

i am trying to output "900,000 milliseconds" in the format "days:hours:minutes:seconds" and I am using this code right now:

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd:HH:mm:ss");
String formatted = simpleDateFormat.format(900000)

900,000 milliseconds should be 15 minutes, so I want it to return

00:00:15:00

or something like this...

But for any reason it returns

01:01:15:00

Can anybody tell me why and how to fix it?

I thought it had to do something with time zones, but it added 1 to the number of days as well...?

Thanks in advance!

Answer 1

Day is 01 because it stands for 01 January. Hour 01 may be related to your time zone. Try this:

SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd:HH:mm:ss");    
simpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String formatted = simpleDateFormat.format(900000);