Matsyapurana 142.6

142.6

pitrye rātryahanī māsaḥ pravibhāgas tayoḥ punaḥ
kṛṣṇapakṣas tvahasteṣāṃ śuklaḥ svapnāya śarvarī //

One month of the human beings is equal to a day and night of the Pitṛis Its division is like this—the dark fortnight is the day of the Pitṛis and the bright one is the night Thirty human months make one month of the Pitṛis The year of the Pitṛis consists of three hundred and sixty human months One hundred human years is equivalent to (31/3) three and one-third years of the Pitṛis (Three Pitṛi years and 120 i e (100+10×2) human months) One human year is equal to one day and night of the Devas and its division is like this—Uttarāyaṇa (six months when the Sun moves towards the north) forms Their day and Dakṣiṇâyana (six months when the Sun moves towards the south) Their night—6 10