Cycle of Four Yugas
Hindu cosmology also stated that when one Manu perishes at the termination of his life, Brahma brings in the next Manu and the cyclic chain continues until all fourteen Manus and the Universe die away by the culmination of the day. When ‘night’ comes about, Brahma goes to sleep for a period of time equivalent to the lives of 14 Manus. The next ‘morning’, Brahma brings to life fourteen yet separate additional Manus in succession, just as he had done on the preceding day. This creating and death cycle goes on for 100 'divine years' at the end of which Brahma himself passes away to oblivion, to be regenerated, thus bring to end this very significant and mystical cycle of the Four Yugas.
However, the Four Yugas possess separate features of their own, often classified as four separate entities. These are as followed:
Satya Yuga (Krita Yuga) - Also referred to as the Golden Age. Satya Yuga had its time specified as 1,728,000 Human years. The method to achieve self-realisation in this Yuga was wholesome meditation on Lord Vishnu. During Satya Yuga, the bulk of the population was situated in the mode of goodness and the average life span in the initiation of the Yuga was 100,000 years.
Treta Yuga - Also referred to as the Silver Age, Treta Yuga had its time span of existence designated as 1,296,000 Human years. The process of self-realisation in this Yuga was the zealous performance of grand yajnas. The average life span was 10,000 years and Godly qualities were reduced to one fourth, as compared to the Satya Yuga. It was also precisely during Treta Yuga that the mode of Varna-Asrama-Dharma was introduced.
Dwapara Yuga - Also referred to as the Bronze Age, Dwapara Yuga had its lifespan designated as 864,000 Human years. The process of self-realisation in this Yuga was ardent and soulful worship of the deities housed and established within temples. Godly qualities amongst humanity were reduced to 50 percent by this epoch and average life expectancy was a mere 1000 years.
Kali Yuga - Also referred to as the Iron Age of hypocrisy and quarrel, Kali Yuga's time of lifespan is designated at 432,000 Human years, from which 5110 years have passed and 426,890 years remain to be lived. Kali Yuga is believed to have begun in 3102 B.C. Lord Krishna had made an appearance in His original, transcendental form right before the culmination of Kali Yuga. The process of self-realisation in the present Yuga is Sankirtan, or chanting of the Holy Names of the Lord.