It is the basic unit of time in both systems.
The SI unit for time is seconds (s).
Fahrenheit is a customary unit
customary
it is in the us customary unit or else we wouldnt be learning about. there for it is in the us customary unit.
Seconds
The customary unit of capacity for a bathtub is gallons.
It is a customary unit.
customary
It is a customary unit.
The unit of time in both the SI and the "customary" systemsis the second.
A Customary Unit or non-SI unit is a measurement unit that is not part of the metric system. Customary units are mainly units of the Imperial system but they could be localised customary units - such as Gaj (for area) is South Asia.