yadā vṛścikādiṣu pañcasu vartate tadāho-rātrāṇi viparyayāṇi bhavanti.

yada-when; vrscika-adisu-headed by Vrscika (Scorpio); pancasu-five; vartate-remains; tada-at that time; ahah-ratrani-the days and nights; viparyayani-the opposite (the duration of the day decreases, and that of night increases); bhavanti-are.