SB 5.21.5

yadā vṛścikādiṣu pañcasu vartate tadāho-rātrāṇi viparyayāṇi bhavanti.
Synonyms: 
yadā — when; vṛścika-ādiṣu — headed by Vṛścika (Scorpio); pañcasu — five; vartate — remains; tadā — at that time; ahaḥ-rātrāṇi — the days and nights; viparyayāṇi — the opposite (the duration of the day decreases, and that of night increases); bhavanti — are.
Translation: 
When the sun passes through the five signs beginning with Vṛścika [Scorpio], the duration of the days decreases [until Capricorn], and then gradually it increases month after month, until day and night become equal [in Aries].