How did we decide on the lengths of various time units?

Question

This a follow up to my earlier question on the lengths of months and weeks.

How did we decide that a second is 1000ms but a minute is 60s and so on

In: 0

Answer 1

We did not decide that a second is 1000 milliseconds. The “milli”, when preceding a unit, always indicates 1 thousandth of the whole unit. So it’s more like we had the second as an unit, and as we needed a finer scale we kind of picked the prefixes that seemed useful in that context, so milli, micro, nano, pico, femto, etc.

Regarding the 60 seconds in a minute, that has historical reasons. Basically because the ancient time measurements that stuck around were built that way.

See

ELI5 why are there 60 seconds in a minute instead of 100?
byu/Plimden inexplainlikeimfive