I have always been confused by the question about if 12 noon was 12 AM or PM. The same goes for midnight; is that 12 AM or PM? Until now I have been able to get by with using the terms midnight or noon to avoid the problem. Everyone knows that those terms mean.
Recently at work I was confronted by the problem of having to deploy software patches to servers between midnight and 1 AM. Simple, right? Not exactly, because the damn software forces one to set all of the time fields xx:xx, including the AM or PM.
To put an end to the issue, I hit Google for an answer. I figured I'd find the answer, write it on a piece of paper, and stick it to one of my monitors so I could refer back to it next month. That's where it got complicated.
An initial quick check of Google gives basically 3 different answers:
1) 12:00 AM and 12:00 PM are not valid concepts.
2) 12:00 AM is midnight
3) 12:00 PM is midnight
Wikipedia's entry is no help. This entry at Greenwichmeantime.com is worthless. Coolquiz.com is totally useless.
This post has a section that shows:
00.00-11.59 is am
12.00-23.59 is pm
This makes sense, but the problem is that the software application isn't going to let me use 00:00, AND it's going to make me pick AM or PM. sheeseh. Crappy software.
After all this reading, now I'm even sure if 12:01 AM or PM is the (almost) the beginning of the new day, or if that's lunchtime. Urgh.
After more reading, I think I have the answer here that shows that 12:01 AM is the start of the day (just after midnight). Going back to my original problem, I can deploy patches at 12:01 AM or 12:05 AM and know that this is just after midnight. Then I can be assured that the server is going to install the patches at night and not at lunchtime.
The root of this problem, I have always believed, is that the new day should start at 1, not 12. Who the hell thought that the day should start with the LAST number and not the first one? The top of the clock should be 1, not 12. But of course me thinking this only clouds the real truth in my own mind. It's just stupid that the day starts, for example around 12:05 AM and then as the day drags on you have 12:57 AM then 1:03 AM, 4 AM, etc.
Why in the heck does it jump from 12 to 1? That's the real root of the problem in my mind.
Using military time on the 24 hour clock makes sense.
I finally did find a good article at nist.gov that confirms my thoughts. It provides good information but starts off by saying:
This is perhaps the trickiest time question of them all. The best answer is that the terms 12 a.m. and 12 p.m. cause confusion and should not be used.
The answer to my question is given in this sentence:
If you are making schedules, times such as 12:01 a.m. (one minute after midnight), or 11:59 p.m. (one minute before midnight) also can eliminate ambiguity. This method is used by the railroads and airlines.
How ironic it is that in our modern society we have to resort to a complete workaround for something as basic and important as time. Yes, the military does it right!