Why Do People Write 0:00AM? What Does it Mean?

Posted by: Josef Essberger
AM means before noon. And PM means after noon. So what the hell is 0:00AM?

Or sometimes they write 0:00PM. Or even 12:00AM. Or 12:00PM. I mean…what do they mean? Is it midnight or noon? I mean, AM means before noon, right? And PM means after noon, right?

But 0:00 is midnight. And 12:00 is noon–or midnight.

Okay, 0:01AM means something. But 0:00AM? Whichever way you look at it, noon is noon and midnight is midnight! How can you be after noon at noon? It doesn’t make sense. Or before midnight at midnight? Suppose they say: “I’ll see you at 12:00AM on Tuesday.” Now you’re stumped. Is that noon or midnight? And if it’s midnight, is it between Monday and Tuesday or between Tuesday and Wednesday?

I mean, really! I suppose logically they must mean between Monday and Tuesday. But it’s not clear! And maybe they mean noon. And I’d hate to turn up at midnight when they meant noon. Or worse still at noon when they meant midnight.

Why do they do that?


Posted by Josef Essberger June 2008
Josef founded EnglishClub for learners and teachers of English in 1997

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