CiviEvent converts times to am on save if lowercase am/pm (%p) is used

If %p, i.e. lower case AM/PM, is used in the time format string, any pm times entered will switch to am upon saving the form.
I have only looked at the "full date" format as that's what seems to be used in the event start/end dates.

This can be reproduced in the sandbox:

• configure date format to use %P (upper case AM/PM)
• configure some event with start or/and end time in the afternoon
• save the form
• open again: all good
• change date format to use %p
• open the event configuration again: still all good
• save the form
• open the form again: time will be am
  q.e.d.