Yuga-Vibhāga and Kāla-Pramāṇa
Measures of Time and the Four Yugas
अहस्तत्रोदगयनं रात्रिः स्याद्दक्षिणायनम् / ये ते रात्र्यहनी दिव्ये प्रसंख्यानं तयोः पुनः
ahastatrodagayanaṃ rātriḥ syāddakṣiṇāyanam / ye te rātryahanī divye prasaṃkhyānaṃ tayoḥ punaḥ
There, the day is called Uttarāyaṇa and the night is Dakṣiṇāyaṇa. And the reckoning of those divine night and day is again set forth.