Sunday, February 18, 2007

A.M. / P.M.

Q. Can you sort out 12:00 a.m. and 12:00 p.m.? In other words, which one means noon and which one means midnight? Mike/Gaylord

A. On air, I gave an answer that I thought was eminently logical. If it’s 11:59 p.m., then the next minute to tick by will take us into the wee hours of the morning, making midnight 12:00 a.m. One minute later, it’s 12:01 a.m.

Correlatively, if it’s 11:59 a.m., 12:00 p.m. (noon) comes next, and a minute later, it will be 12:01 p.m. Piece of cake. Then I went home and did some research.

It turns out that the U.S. Government Printing Office Style Manual puts it precisely the other way around. It says that 12:00 a.m. is noon, and that 12:00 p.m. is midnight.

Thoroughly confused, I sat down and did some thinking. It suddenly hit me that if you consider the nighttime 12:00 as the first minute of the morning, then it makes sense to think of it as a.m. However, if you think of it as the last minute of the evening, logically it’s p.m. The same happens at midday: if 12:00 is the start of the afternoon, then it’s p.m., but if it’s the last minute of the morning, it’s a.m.

So which viewpoint is correct? I have decided to heed the advice of the Greenwich Mean Time site. This summarizes their position: both a.m. and p.m. start at 12:00:01 if you are using a twelve-hour clock, not at 12:00:00. And both a.m. and p.m. end at 11:59:59, not at 12:00:00. Consider this: if you were to write midnight and noon as 6-digit numbers, they would come out as 00:00:00. In other words, they have no meaning; they are ciphers.

I compare it to the yellow stripe down the middle of the highway. That line is not part of the left lane, nor is it part of the right lane. It is the point of demarcation that divides right from left. Likewise, midnight and noon don’t take sides; they are moments of demarcation.

So from now on, there’s no 12:00 a.m. or 12:00 p.m. in my life; it will be noon or midnight. Better yet, perhaps I should switch to the 24-hour clock.

Sidebar: During a discussion, my wife observed that this seems to have become my version of “how many angels can fit on the point of a needle?

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