Noon = 12pm (or 12am) ? – Language lab: English ⇔ German Forums – leo.org

Because of the general confusion about am/pm, mirrored in the comments in this thread, people generally avoid it. This is why car rental companies and so on for which time is important never say your car is due at 12:00, only at 11:59 so they can add a.m. or p.m. and not have to argue with customers.

But to the point itself: I always thought that at exactly noon it is ’12 m.’ (meridiem)–everything before it is ‘a.m.’ and everything after ‘p.m.’. The fact that modern appliance manufacturers force two characters in there and make you decide ‘a’ or ‘p’ doesn’t alter the original derivation, and we are the poorer for being strait-jacketed into this nonsensical discussion.

And calling on the fact that Windows does it one way or the other as support for taking a position is so laughable as to be scarcely worth a response. God help you if Bill Gates is the arbiter of your world–he’s certainly not of mine, even if he tries to insinuate himself into every corner of it.