my $dt   = "2003 % 05 % 1720:55:23";
my $date = sprintf "%d-%02d-%02d", $dt =~ /(\d+) % (\d+) % (\d{2})/;

print "date - $date\n";

__output__

date - 2003-05-17
[download]

That seems to do the trick, but you might also want to check out some of the Date and Time modules for more advanced datetime munging.
HTH

_________
broquaint