Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 1 · Muhurta: Marriage, Home, Farming
ज्योतिःशास्त्रम्
तिथिश्च द्विगुणैकोना कृताङ्गैः करणं निशि ।कृष्णचतुर्दश्यन्ते शकुनिः पर्वणीह चतुष्पदम् ।प्रथमे तिथ्यर्धतो हि किंस्तुघ्नं प्रतिपन्मुखे ॥ २४ ॥
In the full Agni Purana this is chapter 122, verse 24.
Double the tithi (moon day) and take one off. Divided the same way, it gives the karana (half of a moon day) for the night. At the end of the dark 14th comes Shakuni. On the parva (junction day) comes Chatushpada. In the first half of the 1st comes Kimstughna.
Simple meaning: A sum on the moon day gives the half for the night. Fixed halves fall at the month's end and start.
षष्ट्यब्दानां प्रवक्ष्यामि शुभाशुभमतः शृणु ।
In Prabhava there are sacrifice rites. In Vibhava people are happy.
शुक्ले च सर्वसस्यानि प्रमोदेन प्रमोदिताः ।
In Shukla crops are good. Pramoda brings joy. Prajapati brings growth. Angira adds to pleasures.
श्रीमुखे वर्धते लोको भावे भावः प्रवर्धते ।
Shrimukha and Bhava bring growth. Yuva brings heavy rain. Dhata makes plants grow.