Whenever I find myself needing to translate 24-hour time (buying a train ticket in Europe, for example, or anytime someone references a time in a movie about the military), it takes me…way too long. It should be simple math – or memorization, really – but nevertheless, it trips me up. I, and I’m sure many Americans, are much more comfortable with 12-hour time, the “a.m.” and “p.m.” demarcations telling us all we need to know. But…do we know it all?
If I asked you what exactly “a.m.” and “p.m.” stand for, would you know?
Like literally anything else, the abbreviations come from Latin. A.M. means ante meridiem, which translates to “before noon/midday.” So, P.M. means post meridiem – after noon.
The abbreviations have been used since the 17th century, if you can believe it, and the 12-hour clock goes back even further, to the ancient Egyptians. They relied on a sundial to tell time, which, as you can imagine, wasn’t possible after sundown (they’d switch to a water clock at night). But the point remains that their time-telling ability was reliant on the 12-hour timetable.
Next time you want to impress-slash-annoy someone, pull out something like, “Will the event be starting ante meridiem, or post?”