When QTimeEdit is using a locale that has a different format for the am/pm text then it is not possible to change the time via the keyboard directly. This is because it assumes the am/pm text is "am" or "pm" whereas some locales use "a. m." or "p. m.".
The attached example sets it up to use one of those locales automatically.
|For Gerrit Dashboard: QTBUG-72833|
|261806,12||Fix editing of QDateTimeEdit in 12-hour locales that don't use AM/PM||5.13||qt/qtbase||Status: MERGED||+2||0|
|278413,2||QDateTimeParser: always use locale for AM/PM texts||dev||qt/qtbase||Status: MERGED||+2||0|