SB 3.11.12
ayane cahani prahur
vatsaro dvadasa smrtah
samvatsara-satam nrnam
paramayur nirupitam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Two solar movements make one day and night of the demigods, and that combination of day and night is one complete calendar year for the human being. The human being has a duration of life of one hundred years.