I (as someone from europe )would liek to have 24hr format of the time. The 12hr AM/PM is confusing if you are not used to it. 12PM should be after or before 11PM?
I guess its not such a big effort to make two different forms and a config.php entry... or is it?
Then you can edit COM_getHourFormOptions to create a 24 hour time format (or even steal the 1.4.1 version of COM_getHourFormOptions which already is coded).