Use the following format as default time format in Administration→Configuration→International settings.
%I:%M:%S %p Output: 11:43:47 PM
%I:%M:%S %p
%H:%M:%S Uhr Output: 01:51:20 Uhr
%H:%M:%S Uhr
%H:%M Uhr Output: 01:51 Uhr
%H:%M Uhr