Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 1 · Muhurta: Marriage, Home, Farming
ज्योतिःशास्त्रम्
द्वे पिण्डे द्वे च नक्षत्रे नाड्य एकादश ह्यृणे ।वारस्थाने तिथिं दद्यात्सप्तभिर्भागमाहरेत् ॥ ९ ॥
In the full Agni Purana this is chapter 122, verse 9.
Each month add 2 to the pinda (total figure), 2 to the star, and 11 nadis to the minus row. To get the weekday, add the tithi (moon day) to the weekday figure. Divide by seven.
Simple meaning: Each month the figures gain two, two and eleven. Add the moon day and divide by seven for the weekday.
शेषवाराश्च सूर्याद्या घटिकासु च पातयेत् ।
The remainder gives the weekday from Sunday. Add the moon day to the Moon's figure and divide by fourteen.
ऋणं धनं धनमृणं क्रमाज्ज्ञेयं चतुर्दश ।
The fourteen places go minus, plus, plus, minus. The first and thirteenth are five, the second and twelfth ten.
पञ्चदश तृतीये च तथा चैकादशे स्मृतम् ।
The third and eleventh are fifteen. The fourth and tenth are nineteen.