As mentioned over in the Dates thread, this will give you the wrong answer at least one hour a year if you're living in a timezone that switches to and from daylight savings time.

Update: After some research into this (and an experiment with Time::Local), I'm retracting my claim above, at least for the U.S. We do the timezone switch by either repeating 1am on the first Sunday of April, or by dropping 2am on the last Sunday of October. In either case, determining yesterday's date (but not time) can be done safely by subtracting 24 hours from the current time.

Subtracing 24 hours will indeed give the wrong answer during a 1 hour window each year in the U.S. if you're in an area that's doing a daylight savings switch. 

Sat Mar 31 22:00:00 2001 < Sun Apr  1 23:00:00 
Sat Mar 31 23:00:00 2001 < Mon Apr  2 00:00:00 *
Sun Apr  1 00:00:00 2001 < Mon Apr  2 01:00:00

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In reply to Re: Re: How to find yesterdays date (was: Date) by dws
in thread How to find yesterdays date (was: Date) by Anonymous Monk

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