Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
अंशायुः सबले लग्ने तत्साधनमथो शृणु ।गोब्जास्तत्त्वतिथी सूर्यास्तिथिः स्वर्गा नखाः क्रमात् ॥ १२० ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 120.
If the lagna (rising sign) is strongest, use the amshayu (lifespan by degree parts). Now hear how it is worked out. The pinda (total figure) years, Sun to Saturn, are 19, 25, 15, 12, 15, 21 and 20.
Simple meaning: If the rising sign is strongest, the degree method is used. Full years for each planet are listed.
नखा विधुर्द्वावंकाश्च धृतिः स्वाक्षिखमार्गणाः ॥ १२१ ॥
The natural years for each planet are listed.
पिंडे निसर्गे रवोच्चे नो ग्रहः षट्भाल्पको यदा ।
A planet's full years count by how far it stands from its low point.
अंशोनाः शत्रुभे कार्या ग्रहं वक्रगतिं विना ।
A planet's years are reduced when it is in an enemy sign or set in the Sun's light.