Markandeyapurana 46.38

46.38

caturdaśaguṇo hyeṣa kālo brahmyamahaḥ smṛtam /
tasyānte pralayaḥ prokto brahman naimittiko budhaiḥ //

In one of Brahmā’s days, O brahman, there may be fourteen Manus. They live according to their portions; that thousand is divided among them. The gods, the seven ṛṣis, and Indra, Manu, and the kings his sons, are created with Manu and pass to dissolution with him in regular order. Seventy-one repetitions of the four ages, with a fraction in excess, constitute a manvantara; hear from me its computation in human years. Thirty full crores reckoned duly, O brahman, and sixty-seven lakhs more by reckoning, and twenty thousands—this is the period of seventy-one times the four ages without the excess fraction; this is called a manvantara. Hear it from me in divine years; eight hundred thousands of years by divine reckoning,[9] and fifty-two thousands of years more in addition. A day of Brahma is declared to be this period multiplied fourteen times.[10] At its termination the dissolution is declared by the wise to be the necessary result, O brahman.