++tilly on the ISO date advocacy post.

I'm not a big fan of using sprintf or other home-grown methods for formatting date strings. IMHO, it's much cleaner to use CPAN's Date::Format module. You get clearer code, and more consistent results:

#!/usr/bin/perl -w

use strict;
use Date::Format;

my $iso_date = time2str '%Y-%m-%d', time;
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This will return the date in ISO format: YYYY-MM-DD