[mark-r]

That's just a cop-out. If you change the question from 11 AM to 11:01 AM it's still just as valid, and there's no need to argue about the ambiguity. Is there anybody who would seriously argue that 12:00 AM plus one minute should be 12:01 PM? That way lies madness.

[naikrovek]

12:00 isn't AM or PM. It straddles them, and isn't wholly either one because of it. That's what this is about. Some people could argue that noon is 12AM. Others can argue that it's 12PM. Both views have merit, and despite that, we need to agree on one or the other, because times are often written down and everyone needs to know what time is meant when someone writes "12AM." Since consensus on this has never been achieved, we just decided on something that people COULD agree on: noon and midnight.

The question isn't valid for 11AM vs 11:01AM, because crossing into 11:01AM doesn't put you into the afternoon like 12:01PM does. It's only a valid question at the transition time between AM and PM or vice versa. So, it was decided a LONG time ago to just skip the problem and say "twelve noon" or "midnight" (or "twelve midnight".)

[goialoq]

AM means "before noon". PM means "after noon"

12:00 noon is neither AM nor PM, and there'se no confusion.

The real question is why is the hour after midnight 12:01-12:59 AM.

Anyway, the real answer is that 0/12 and 13/1 are partial branch cuts and that "12" is used because "0" is awkward for mundane reasons, but retains some of its "0-ness"

https://en.wikipedia.org/wiki/Branch_point

[mark-r]

I'm not disagreeing that "noon" or "midnight" are less confusing, I'm simply saying there shouldn't be any ambiguity about 12AM or 12PM in the first place.

Any potential for confusion results from an ancient decision to designate noon/midnight as 12:00. If they had simply made them 1:00 instead then there'd be no trouble today.