Yuga-Vibhāga and Kāla-Pramāṇa
Measures of Time and the Four Yugas
चतुः साहस्रयुक्तं वै प्राकृतं तत्कृतं युगम् / त्रेताशिष्टं प्रवक्ष्यामि द्वापरं कलिमेव च
catuḥ sāhasrayuktaṃ vai prākṛtaṃ tatkṛtaṃ yugam / tretāśiṣṭaṃ pravakṣyāmi dvāparaṃ kalimeva ca
The primal Kṛta-yuga is indeed set with four thousand; now I shall declare as well what remains—Tretā, Dvāpara, and Kali.