Yuga in Hindu philosophy is the name of an `epoch` or `era` within a cycle of four ages. These four ages are named as the Satya Yuga, Treta Yuga, Dvapara Yuga and Kali Yuga. According to Hindu cosmology, the world is created, destroyed and recreated every 4,320,000 years. Each yuga from within the four yugas, is an age with distinctive features in which incarnations of Krishna manifest themselves. The four yugas make up a cycle called divya-yuga, which lasts for 4,320,000 years.

If embracing and following strictly by the Hindu mythology and cosmology, the cosmos (universe) is created in a cyclic manner, which is then destructed after the culmination of its lifespan. The life span of Brahma, the creator as is conceived by Hindu mythology, is 100 years of Brahma. One day in the life of Brahma is referred to further as a Kalpa. On every Kalpa (one single day in the life of Brahma), Brahma is believed to form fourteen Manus one after another, who in turn reveal their presence and control the physical world. Therefore, there exists fourteen generations of Manu in each Kalpa or day of Brahma, the creator. Herein comes the factor of the four yugas and how they are integrally linked with Brahma and his inventions.

Each Manu`s life (Manvantara) consists of 71 Chaturyugis (tetrads of eras). Each Chaturyugi is complied of four eras or Yugas: Satya, Treta, Dwapara and Kali. The span of Satya Yuga is 1,728,000 human years, Treta Yuga is 1,296,000 human years, Dwapara Yuga is 864,000 human years and Kali Yuga is 432,000 human years. 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 fourteen 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.

Yuga (referred to yug in Devanagari script) in Hindu philosophy refers to the name of an `epoch` or `era` within a cycle of four ages (or, as is being discussed, four yugas). The four basic yugas comprise the Satya Yuga (also referred to as Krita Yuga), the Treta Yuga, the Dwapara Yuga and eventually, the Kali Yuga. Stated in the line of Hindu cosmology, the world is created, destructed and again recreated every 4,320,000 years (Maha Yuga). The cycles are conceived to repeat in a cyclic manner, just like the seasons, waxing and waning amidst a bigger time-cycle of the creation and devastation of the universe. Just like in Summer, Spring, Winter and Autumn, the four yugas engage themselves into stages or gradual changes, which the earth and the perception of mankind goes through as a whole. A complete yuga cycle from a high Golden Age (acknowledged as a period of peace, harmony, stability and prosperity. In literary compositions, the Golden Age generally culminates with an annihilating event, which brings about the Fall of Man) of enlightenment to a Dark Age and back again is unanimously believed to be induced by the solar system`s rotation and revolution around a central sun.

Amongst the four cardinal yugas designated by Brahma, the present epoch is the Kali Yuga, or last era in one of the 71 Chaturyugis (set of four Yugas or eras) in the life one of fourteen Manus. The current Manu is assumed to be the seventh Manu and his name is also acknowledged as Vaivasvat. According to Aryabhata, the Kali Yuga had taken its first rotational step in 3102 B.C., at the termination of the Dwapara Yuga, which was marked by the sudden fading of Vishnu`s Krishna avatar. Aryabhata`s date is henceforth, extensively echoed in present day Hinduism. The beginning of the new Yuga (era) is known as "Yugadi/Ugadi", and is commemorated every year on the first day (Paadyami) of the first month (Chaitramu) of the 12-month yearly cycle. The Ugadi of 1999 starts the year 1921 of the Shalivahana era (5101 Kali Yuga, 1999 A.D.). The termination of Kali Yuga is 426,899 years from 1921.

However, the four distinctive 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 (sacrifices). 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. In this context, the exceedingly unique point to notice is that, C.E. 2008 had corresponded to Kali yuga year 5110. Lord Krsna (pertaining to 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 sankirtana, or chanting of the Holy Names of the Lord. God consciousness in Kali yuga is reduced to 25 percent of the population and life expectancy is just 100 years. By now, already 5000 years of Kali yuga have passed and it is also presaged that by the end of the yuga, people will scarcely be older than 20 years and their sole nutrient would be meat.