Why does new Date() sometimes use different timezone?

Question

I have date values stored as longs (milliseconds). I debug my app because I somehow get time parts that are not zero (00:00:00). Then I noticed this:
315529200000 : Tue Jan 01 00:00:00 CET 1980
1104447600000 : Fri Dec 31 00:00:00 CET 2004
1059602400000 : Thu Jul 31 00:00:00 CEST 2003
All values have a time of zero (correct) but show a diffetent time zone? How is that possible? I created the time strings all via the same
Systemn.out.println("Date of long: "+new Date(l));
The last number suddenly hast "CEST" instead of "CET" and therefore somewhere else lead to a time 23:00:00.

Answer 1

I just checked this simple case:
I have a date and add exactly 1 day and the result is not the original result + 1 day:
        long d1 = 1099173600000L; //2004-10-31 00:00:00
        System.out.println(new Date(d1));
        long d2 = 86400000L; //1 day in milliseconds
        long d3 = d1 + d2;
        System.out.println(new Date(d3)); //2004-10-31 23:00:00 !!!
]/code]
the output is:
Sun Oct 31 00:00:00 CEST 2004
Sun Oct 31 23:00:00 CET 2004
So, instead of added 1 day, this just added 23 hours!