note 124048 added to dateinterval.format

I'm trying to get the difference of two dates in months, but I get such a surprise (5 months instead of 19 months): $date_start = new DateTime("2018-01-01"); $date_stop = new DateTime("2019-07-18"); $interval = $date_start->diff($date_stop); echo $interval->format("%r%m"); // 5 print_r($interval); DateInterval Object ( [y] => 1 [m] => 6 [d] => 16 [h] => 0 [i] => 0 [s] => 0 [f] => 0 [weekday] => 0 [weekday_behavior] => 0 [first_last_day_of] => 0 [invert] => 0 [days] => 563 [special_type] => 0 [special_amount] => 0 [have_weekday_relative] => 0 [have_special_relative] => 0 ) ---- Server IP: 208.43.231.9 Probable Submitter: 185.85.3.195 (proxied: 185.46.221.251) ---- Manual Page -- http://php.net/manual/en/dateinterval.format.php Edit -- https://master.php.net/note/edit/124048 Del: integrated -- https://master.php.net/note/delete/124048/integrated Del: useless -- https://master.php.net/note/delete/124048/useless Del: bad code -- https://master.php.net/note/delete/124048/bad+code Del: spam -- https://master.php.net/note/delete/124048/spam Del: non-english -- https://master.php.net/note/delete/124048/non-english Del: in docs -- https://master.php.net/note/delete/124048/in+docs Del: other reasons-- https://master.php.net/note/delete/124048 Reject -- https://master.php.net/note/reject/124048 Search -- https://master.php.net/manage/user-notes.php