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© Copyright 1998, Jim Loy
I went to Pizza Hut at about 1 A.M., because they had a sign on the door that said they were open from 12 A.M. to 12 P.M. Of course, 12 A.M. is midnight, and 12 P.M. is noon. Believe me. I did not notice that those are pretty stupid hours for a restaurant, and an obvious mistake. It was embarrassing that I didn't figure that out.It could have been worse, 12 A.M. to 1 A.M., for example.
The reason for all this is that 12:00 is used as zero. Logically, we need a 0:00 on our watches and clocks. 12:30 A.M. is obviously 30 minutes after midnight. So, everyone already uses 12:30 as 0:30. We just get confused about the two borders between A.M. and P.M., midnight and noon.
Much of the world uses a 24 hour clock, noon is 1200 hours. I don't remember if they use 000 for midnight, or 2400 (I suspect it is 2400, so their clock would go up to 2459, and they would have the same confusion that we do at midnight).
Professional astronomers who use telescopes (there are other astronomers), use noon as the beginning of the day, and use a twenty-four hour clock. They do this so that the day does not change (from Monday to Tuesday, for example) in the middle of an observation. That would complicate their records, and their arithmetic.
Addendum:
Actually, there seems to be some ambiguity going on, with the 24 hour clock. Both 0000 and 2400 are often used, even by the same people in the same sentence (as "... from 0000 to 2400"). So you may see 2400. But you won't see 2459 (0059 instead).
About my objection to not having a zero, when we count objects, we usually start at one, not zero. But when we measure quantities, including time, we start at zero. Starting at one (or 24) only complicates the entire process. We can deal with it, as we in fact do deal with it. But zero would be simpler.