Vishnupurana 1.3.25

1.3.25

janasthair yogibhir devaś cintyamāno 'bjasaṃbhavaḥ
tatpramāṇāṃ hi tāṃ rātriṃ tadante sṛjate punaḥ //

Seven Rishis, certain (secondary) divinities, Indra, Manu, and the kings his sons, are created and perish at one period; and the interval, called a Manwantara, is equal to seventy-one times the number of years contained in the four Yugas, with some additional years: this is the duration of the Manu, the (attendant) divinities, and the rest, which is equal to 852.000 divine years, or to 306.720.000 years of mortals, independent of the additional period. Fourteen times this period constitutes a Bráhma day, that is, a day of Brahmá; the term (Bráhma) being the derivative form. At the end of this day a dissolution of the universe occurs, when all the three worlds, earth, and the regions of space, are consumed with fire. The dwellers of Maharloka (the region inhabited by the saints who survive the world), distressed by the heat, repair then to Janaloka (the region of holy men after their decease). When the-three worlds are but one mighty ocean, Brahmá, who is one with Náráyańa, satiate with the demolition of the universe, sleeps upon his serpent-bed--contemplated, the lotus born, by the ascetic inhabitants of the Janaloka--for a night of equal duration with his day; at the close of which he creates anew. Of such days and nights is a year of Brahmá composed; and a hundred such years constitute his whole life. One Parárddha, or half his existence, has expired, terminating with the Mahá Kalpa called Pádma. The Kalpa (or day of Brahmá) termed Váráha is the first of the second period of Brahmá's existence.