Yuga-Vibhāga and Kāla-Pramāṇa
Measures of Time and the Four Yugas
तत्राहः कर्मचेष्टायां रात्रिः स्वप्नाय कल्पते / पित्र्ये रात्र्यहनी मासः प्रविभागस्तयोः पुनः
tatrāhaḥ karmaceṣṭāyāṃ rātriḥ svapnāya kalpate / pitrye rātryahanī māsaḥ pravibhāgastayoḥ punaḥ
There, the day is ordained for the striving of deeds, and the night is appointed for sleep and dream. In the realm of the Pitṛs, night and day together make a month; and again their division is set forth.