परमायुर्निरूपितम् ॥ १२ ॥
vatsaro dvādaśa smṛtaḥ
ayane — in the solar movement (of six months); ca — and; ahanī — a day of the demigods; prāhuḥ — it is said; vatsaraḥ — one calendar year; dvādaśa — twelve months; smṛtaḥ — is so called; saṁvatsara-śatam — one hundred years; nṝṇām — of human beings; parama-āyuḥ — duration of life; nirūpitam — is estimated.
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.