I'd probably select Time::Local there. There's a gotcha or two to lookout for though.

my ($S, $M) = (0,0);
my $H = $1 if $hour =~ m/0*(\d+)/; # I'm not sure if leading 0s hurt
my $d = $1 if $day =~ m/0*(\d+)/;
my $m = $1 if $month =~ m/0*(\d+)/;
   $m --; # gotcha!  the month is 0-11

# timelocal($sec,$min,$hour,$mday,$mon,$year);
my $utime = timelocal($S, $M, $H, $d, $m, $year);
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Although, in general, Date::Manip is the way to go, timelocal is a million times faster.