Why is 00:00 called midnight?

Why Is 00:00 Called Midnight?

Ever wonder why 00:00 is called midnight? It’s a quirk of language, history, and how we’ve chosen to divide the day. The answer lies in Latin—and a bit of timekeeping tradition.

The terms a.m. and p.m. come from Latin: ante meridiem and post meridiem, meaning “before midday” and “after midday,” respectively. Since midday is 12:00 noon, the cycle needs a starting point—and that’s where midnight comes in.

Midnight, or 00:00, marks the beginning of a new day. But instead of calling it 12:00 p.m., which would create confusion with noon, it was decided that the stroke of midnight would be labeled 12:00 a.m. This might seem backwards—after all, how can midnight be “before midday”?—but it makes sense when you think of it as the first moment before the next noon.

So, 00:00 is midnight because it’s the precise point when the clock resets, and the cycle of a.m. begins anew. It’s both the end of one day and the start of the next, quietly bridging two dates in a single breath.

Interestingly, this labeling can still cause mix-ups. For example, saying “12 a.m.” without context might leave someone wondering if you mean midnight at the start or end of a day. That’s why event planners and airlines often use “11:59 p.m.” or “12:01 a.m.” to avoid confusion.

Still, despite the occasional ambiguity, calling 00:00 “midnight” or “12 a.m.” remains a quiet nod to the ancient roots of how we measure time—anchored in Latin, shaped by convention, and lived by billions every single day.