"Prakriti" (primal matter) remains mixed for a "maha-kalpa" (life of Brahma) of 311.04 trillion years, and is followed by a "maha-pralaya" (great dissolution) of equal length. The universe (matter) remains manifested for a "kalpa" (day of Brahma) of 4.32 billion years, where the universe is created at the start and destroyed at the end, only to be recreated at the start of the next "kalpa". A "kalpa" is followed by a "pralaya" (partial dissolution, night of Brahma) of equal length, when Brahma and the universe are in an unmanifested state. Each "kalpa" has 15 "manvantara-sandhyas" (junctures of great flooding) and 14 "manvantaras" (age of Manu, progenitor of mankind), with each "manvantara" lasting for 306.72 million years. Each "kalpa" has 1,000 and each "manvantara" has 71 "chatur-yugas" (epoch, "maha-yuga"), with each "chatur-yuga" lasting for 4.32 million years and divided into four "yugas" ("dharmic" ages): "Satya Yuga" (1,728,000 years), "Treta Yuga" (1,296,000 years), "Dvapara Yuga" (864,000 years), and "Kali Yuga" (432,000 years), of which we are currently in "Kali Yuga".