I'd like to point out that this solution will also not work when the timezone is 12 or more hours on either side of GMT (I believe there are some that are off by 13 hours). It's probably best to stick with Date::Calc.

$ date; TZ=GMT0 date       
Wed Jun  9 12:01:15 EDT 2004
Wed Jun  9 16:01:15 GMT 2004
$ TZ=GMT-12 perl foo.pl
06/09/2004
$ TZ=GMT+12 perl foo.pl
06/08/2004
$ TZ=GMT-13 perl foo.pl
06/09/2004
$ TZ=GMT+13 perl foo.pl
06/07/2004
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