Time::Piece makes it fairly easy, but you would have to benchmark it against other solutions to see what works for you. How much data are you dealing with?
use Time::Piece;
use strict;
use warnings;
my $date = '20070301103000';
my $start = Time::Piece->strptime($date, "%Y%m%d%H%M%S")->epoch;
print $start, "\n";