Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 32

Sanskrit:

तत्पुत्रपौत्रनप्तृणां गोत्राणि च न श‍ृण्महे ।कालोऽभियातस्त्रिणवचतुर्युगविकल्पित: ॥ ३२ ॥

ITRANS:

tat putra-pautra-naptṝṇāṁgotrāṇi ca na śṛṇmahekālo ’bhiyātas tri-ṇava-catur-yuga-vikalpitaḥ

Translation:

Twenty-seven catur-yugas have already passed. Those upon whom you may have decided are now gone, and so are their sons, grandsons and other descendants. You cannot even hear about their names.

Purport:

During Lord Brahmā’s day, fourteen Manus or one thousand mahā-yugas pass away. Brahmā informed King Kakudmī that twenty-seven mahā-yugas, each consisting of the four periods Satya, Tretā, Dvāpara and Kali, had already passed. All the kings and other great personalities born in those yugas had now departed from memory into obscurity. This is the way of time as it moves through past, present and future.