Srimad-Bhagavatam

Canto 3 Chapter 11 Text 3 

By His Divine Grace A C Bhaktivedanta Swami Prabhupada

TEXT 3

One can estimate time by measuring the movement of the atomic combination of bodies.

Time is the potency of the almighty Personality of Godhead, Hari, who controls all physical movement although He is not visible in the physical world.