Well, localtime also gives you the hours, minutes, and seconds, but through the power of slices, you've skipped over them in your assignment to the @f array.

use strict;
use warnings;


my @f = ( localtime )[0..5];
my $system_date = sprintf "%d" . "%02d" x 5,
    $f[5] + 1900,
    $f[4] + 1,
    @f[ 3, 2, 1, 0 ];


print $system_date, "\n";
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Check the POD for localtime. Also, you may find perldata interesting as it discusses the use of slices. Oh, and I used the 'x' operator (see perlop) and the '.' concatenation operator (also found in perlop) to reduce the sprintf template to something more understandable.