Bhagavad Gita 8.25

धूमो रात्रिस्तथा कृष्ण: षण्मासा दक्षिणायनम् |
तत्र चन्द्रमसं ज्योतिर्योगि प्राप्य निवर्तते

Translation

The yogi returns (to the world) after attaining the light of the moon through the six-monthly path of Dhoom, Ratri, Krishnapaksh and Dakshinayan.