When doing a lot of these calculations with dates, keeping the dates in a standard localtime list can prove very useful. When iso-dates are to be generated like in this example, calculation is faster than printf:

use Benchmark qw(cmpthese);

my @d = localtime;
cmpthese (-1, {
    prnt  => sub {
        my $x = sprintf "%d%02d%02d", 1900 + $d[5], $d[4] + 1, $d[3];
        },
    calc  => sub {
        my $x = (($d[5] + 1900) * 100 + $d[4] + 1) * 100 + $d[3];
        },
    });

=>

          Rate prnt calc
prnt 2025658/s   -- -37%
calc 3215550/s  59%   --
[download]

And yes, I did have a long running process where millions of these were done, so it did matter.