use warnings;
use strict;
use DateTime;

my $dt1 = DateTime->new(year => 2013, month => 10, day =>  1);
my $dt2 = DateTime->new(year => 2018, month =>  3, day => 31);

my $dur1 = $dt2->subtract_datetime($dt1);
print $dt1->ymd, " to ", $dt2->ymd, ": ",
	$dur1->months, " months - oops!\n";

my ($days,$months) = $dur1->in_units('days','months');
print $dt1->ymd, " to ", $dt2->ymd, ": ",
	"$months months, $days days", "\n";

__END__

2013-10-01 to 2018-03-31: 5 months - oops!
2013-10-01 to 2018-03-31: 53 months, 30 days