Rather than time(), I'd suggest using...

use Time::Local;
my $time = timelocal(0, 0, 12, (localtime)[3, 4, 5]);
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This'll make midday your starting point for calculations, which helps sidestep the whole daylight savings issue Smylers pointed out.

As an added bonus, Time::Local is also part of the core distribution, so you don't need to install anything via CPAN (which is good, as some of those other more fancy Date:: modules are mighty bloaty!).