Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
याम्यायने स्थिरे त्वाद्याः पराः सौम्येन्दुमूर्तिभैः ।मेध्या विषुवति प्रोक्ताः पुण्यनाड्यस्तु षोडश ॥ २६४ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 264.
In the southern course and in fixed signs, the earlier ghatika (24-minute unit) are holy. In the northern course and in 'indumurti' signs, the later ones are holy. At the equinox, sixteen holy ghatikas are named as pure. (Our text is unclear here: which signs 'indumurti' names.)
Simple meaning: Holy hours fall before or after the Sun's entry, by its course and sign. Sixteen ghatikas are holy.
संध्या त्रिनाडी प्रमितार्कबिंबोर्द्धोदयास्ततः ।
Twilight lasts three ghatikas. An entry in twilight moves its holy time to the day before or after.
यादृशेनेंदुना भानोः संक्रांतिस्तादृशं फलम् ।
The Moon's state at the Sun's entry decides whether the entry is good or bad for a person.
संक्रांतेः परतो भानुर्भुक्त्वा यावद्भिरंशकैः ।
After the Sun enters a sign and covers some degrees, the next turn of its course follows.