What is time and it si unit

the duration between any two events is called time. It's si unit is second.

Time: The concept of time is self-evident. An hour consists of a certain number of minutes, a day of hours and a year of days. Time is represented through change, such as the circular motion of the moon around Earth. The passing of time is indeed closely connected to the concept of space.

The SI unit for time is second: The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the cesium frequency ΔνCs, the unperturbed ground-state hyperfine transition frequency of the cesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s-1.