sahasra-yuga-paryantam ahar yad brahmano viduh। ratrim yuga-sahasrantam te ’ho-ratra-vido janah॥ 8.17 ॥

By human calculation, a thousand ages taken together form the duration of Brahma’s one day. And such also is the duration of his night.

{
A Year of Man = A Day of the Deities

( Daytime of the Deities = = The six-month period of the sun towards the north – Utrayanam )
( Night time of the Deities = = The six-month period of the sun towards the south – Tatcinayanam )
365 Year of the Deities = 1 Year of the Deities
4800 Year of the Deities = Kridha Yuga / Satya Yuga
3600 Years of the Deities = Dretha Yuga
2400 Years of the Deities = Dwapara Yuga
1200 Years of the Deities = Kali Yuga
12000 Years of Deities = 1 Sutur Yuga
1000 Sutur Yuga = One Day of Brahmana
1000 Sutur Yuga = One Night of Brahmana
14 Manu's will lead the universe
One Manu's Period = One Manvantra
Brahma's One Day + Brahma's One Night = Brahma's Day
Brahma's 365 days = Brahma's one year
Brahmma's lifetime = 100 Brahma years
Brahmma's lifetime end = mahabralayam (destruction of the whole world)
In the end of Brahmma's life, the Mahapralayam will take place. Then Brahmma will be destroyed. Thereafter there will be no form of 100 Brahmma years. Then Lord Vishnu will again make a Brahma. Then the creation will continue.

Kalpam / Creation = Brahmma's one day time = 4320 million human years
Brahmayam / Destruction = Brahmins one night time = 4320 million human years

The cycle of a four-yuga cycle is a thousandth occurrence called Kalpam.
Satya Yuga = 1728,000 Human Years: 100% Good People; 0% evil People
Dretha Yuga = 1296,000 Human Years: 75% of Good People; 25% evil People
Dwapara Yuga = 864,000 Human Years: 50% of Good People; 50% evil People
Kaliyuga = 432,000 Human Years: 25% of Good People; 75% evil People

Each Kalpam is divided into 14 Manvantra (time).
Every Manvantra will last about 71 cycles.
The Manu's is Head in every Manthandra.
}