# calculate data on run time to even previous hour
my $dt = POSIX::strftime("%Y-%m-%d", localtime( shift( @_ ) || time ) );
my $hr = POSIX::strftime("%H", localtime( shift( @_ ) || time ) );
my $bhr = $hr - 1;
my $bdt = "$dt $bhr:00:00";

# this one comes from the DB but it looks like this
my $db_date = "2015-04-08 12:42:13";

# this is what I want to do
if ($db_date <= $bdt) {
    # process
}