my $format = DateTime::Format::Strptime->new(
    pattern   => '%Y-%m-%d %H:%M:%S',
    time_zone => 'local',
);

my $min_start = DateTime->new( year => 2007, month => 5, day => 1, time_zone => 'local' );
my $max_stop  = DateTime->new( year => 2008, month => 5, day => 1, time_zone => 'local' );

##</code><code>##

my $start = $format->parse_datetime(...);
my $stop  = $format->parse_datetime(...);

$start = $min_start if $start < $min_start;
$stop  = $max_stop  if $stop >= $max_stop;

my $dur = $start->delta_ms($stop);

printf("%d minutes and %d seconds\n", $dur->in_units(qw( minutes seconds ));