h
hour
Timeexact by definition
The hour is exactly 3,600 seconds, that is 60 minutes. It is not an SI unit but is accepted for use with SI, and the factor is exact by definition. It anchors a large family of derived units including km/h, kWh and air changes per hour.
| 1 h | 3,600 s |
Where the unit came from
The 24-hour day comes from Egyptian practice of dividing daylight and night into twelve parts each. Those hours originally varied in length with the seasons, since daylight does, and the fixed hour of equal length came later with mechanical clocks.
Solvers that use time