Śrīmad-Bhāgavatam 3.11.18
SB 3.11.18
Open the full passageSanskrit
maitreya uvāca kṛtaṁ tretā dvāparaṁ ca kaliś ceti catur-yugam divyair dvādaśabhir varṣaiḥ sāvadhānaṁ nirūpitam
Translation
Maitreya said: O Vidura, the four millenniums are called the Satya, Tretā, Dvāpara and Kali yugas. The aggregate number of years of all of these combined is equal to twelve thousand years of the demigods.