We Germans, and I think most Europeans are the same, don’t use a.m. and p.m. time formats. We more or less know what they mean (something like “7 p.m.” is easy but I personally can’t tell you if 12 p.m. is noon or midnight). But we don’t use a.m. / p.m. “officially”. Every timestamp or every mention of a time on any website or any email is in 24 hour format. So when we (and our users) see the a.m. / p.m. format in the new Events module, we are very irritated.
That’s why I propose that every community gets to choose if they want to show the a.m. / p.m. format (Hello USA!) or the 24h format (Hello almost everyone else!). I also propose that every community can set a default time zone - because many countries worldwide only have one and there is no need to set it each time an event is created.