Measures: Time — how long something takes
Day
One turn of the Earth, standardized.
TimeHow it's defined
Defined as exactly 86,400 seconds. The Earth itself is a slightly sloppy clock — its rotation wobbles by milliseconds — so the day is pinned to the atomic second, and leap seconds patch the difference.
Convert — honestly
86400 s
Second · factor exact — the base unit itself
1440 min
Minute · factor exact — exact by definition
24 h
Hour · factor exact — exact by definition
Conversions run through the second using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
Other ways to measure time
Source
This page is an authored summary of the authoritative definition — checkable one click away.
BIPM — The International System of Units (SI Brochure, 9th ed.)