I think the problem is that under cygwin localtime returns GMTime.

There's a solution here:

http://www.mail-archive.com/cygwin@cygwin.com/msg37313.html

which says "use POSIX 'tzset'; tzset()" before calling localtime.

I haven't tested it. So use at your own risk.

-XorL

Update: just fixed a typo.