Standards of Weights and Measures Act : Base unit of time. Indian Bare Acts :

Standards of Weights and Measures Act,1976

Act No : 60

Section : Base unit of time.

7. Base unit of time. (1) The base unit of time shall be the second. (2) The "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.