Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
सौम्यायनं मासषट्कं मृगाद्यं भानुभुक्तितः ।अहः सुराणां तद्रात्रिः कर्काद्यं दक्षिणायनम् ॥ १२५ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 125.
The six months starting with Capricorn, by the Sun's passing, are uttarayana (the Sun's northward course). That is the day of the gods. Their night is dakshinayana (the Sun's southward course), starting with Cancer.
Simple meaning: The Sun's northward half-year starts at Capricorn and is the gods' day. The southward half starts at Cancer and is their night.
गृहप्रवेशवैवाहप्रतिष्ठामौंजिबंधनम् ।
House entry, marriage, installing a deity and the thread ceremony suit the Sun's northward half-year, from Magha.
याम्यायने गर्हितं च कर्म यत्नात्प्रशस्यते ।
In the Sun's southward half these acts are blamed, allowed only with great care. Each season lasts two months from Magha.
मृगाच्छिशिरवसंतश्च ग्रीष्माः स्युश्चोत्तरायणे ।
Three seasons fall in the Sun's northward half and three in the southward half.