Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 6 · Calendar, Muhurta Elements
कालमानं मुहूर्ताङ्गानि च
नामतुल्यफलाः सर्वे विज्ञेयाः षष्टिवत्सराः ।युगं स्यात्पंचभिर्वर्षैर्युगान्येवं तु द्वादश ॥ १२१ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 121.
All sixty years are to be known as giving results like their names. A yuga (five-year cycle) is made of five years. So there are twelve yugas.
Simple meaning: Each of the sixty years gives results like its name. Five years make a cycle, so there are twelve cycles.
तेषामीशाः क्रमाज्ज्ञेया विष्णुर्देवपुरोहितः ।
The twelve five-year cycles have lords. The first six are Vishnu, Jupiter, Indra, Lohita, Tvashta and Ahirbudhnya.
पितरश्च ततो विश्वे शशींद्राग्न्यश्विनो भगः ।
The last six cycle lords are named. The five years inside each cycle are ruled by Agni, Sun, Moon, Brahma and Shiva.
अथाद्वेशचमूनाथसस्यपानां बलाबलम् ।
Check the strength of the year's lord, army chief and crop lord, and the planets' movement. Then give the result.