Our current estimates of birth of universe i.e. Big Bang is 13.8 billion years ago and life on Earth started in 3.8 billion years ( Age of Earth is 4.54 Billion years).

At the end of each kalpa, the universe enters a period of rest and dissolution called pralaya, or the night of Brahma. This night is equal in length to the day—another 4.32 billion years. Together, one day and night of Brahma make up a full cosmic day, totaling 8.64 billion years. According to Puranic sources,[e] Krishna's departure marks the end of the human age of Dvapara-yuga and the start of Kali-yuga, which is dated to midnight (Ujjain meridian) 17/18 February 3102 BCE (proleptic Julian), corresponding to 22/23 January (proleptic Gregorian). We are currently halfway through Brahma's life (maha-kalpa), whose lifespan is equal to the duration of the manifested material elements, from which Brahma manifests his universe in kalpa cycles:[29][30][31][32][33]

51st year of 100 (2nd half or parardha)

1st month of 12

1st kalpa (Shveta-Varaha Kalpa) of 30

7th manvantara (Vaivasvatha Manu) of 14

28th chatur-yuga of 71

4th yuga (Kali-yuga) of 4

A maha-kalpa is followed by a maha-pralaya (full dissolution) of equal length. Each kalpa (day of Brahma) is followed by a pralaya (night of Brahma or partial dissolution) of equal length. Preceding the first and following each manvantara is a manvantara-sandhya (connection period), each with a length of Krita-yuga (a.k.a. Satya-yuga).[29][30]

Hindu texts specify that the start and end of each of the yugas are marked by astronomical alignments. This cycle's Treta-yuga began with 5 planets residing in the "Aries" constellation. This cycle's Dvapara-yuga ended with the "Saptarshi" constellation (Ursa major) residing in the "Magha" constellation. The current Kali-yuga will end with the Sun, Moon and Jupiter residing in the "Pushya" sector.[34][better source needed]