Time quantifies or measures the interval between events, or the duration of events. (wikipedia)

The standard unit for time is the SI second.

A second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

We use larger units: minute, hour, day, week, month, year, century.

Those additional units make things hard.