Yuga in Hinduism is an epoch or era within a four-age cycle. A complete Yuga starts with the Satya Yuga, via Treta Yuga and Dvapara Yuga into a Kali Yuga Our present time is dvapara yuga.
There are four Yugas in one cycle:
Characteristics of each Yuga
- Satya Yuga (also known as Krita Yuga "Golden Age"): The first and best Yuga. It was the age of truth and perfection. This Yuga has Zero Percent of Crime and Hundred Percent of Kindness. The Krita Yuga was so named because there was but one religion, and all men were saintly: therefore they were not required to perform religious ceremonies. Humans were gigantic, powerfully built, honest, youthful, vigorous, erudite and virtuous. The Vedas were one. All mankind could attain to supreme blessedness. There was no agriculture or mining as the earth yielded those riches on its own. Weather was pleasant and everyone was happy. There were no religious sects. There was no disease, decrepitude or fear of anything.
- Treta Yuga: Is considered to be the second Yuga in order, however Treta means the "Third". In this age, virtue diminishes slightly. At the beginning of the age, many emperors rise to dominance and conquer the world. Wars become frequent and weather begins to change to extremities. Oceans and deserts are formed. People become slightly diminished compared to their predecessors. Agriculture, labour and mining become existent.
- Dvapara Yuga: Is considered to be the third Yuga in order. Dvapara means "two pair" or "after two". In this age, people become tainted with Tamasic qualities and aren't as strong as their ancestors. Diseases become rampant. Humans are discontent and fight each other. Vedas are divided into four parts. People still possess characteristics of youth in old age. Average lifespan of humans is around a few centuries.
- Kali Yuga: The final age. It is the age of darkness and ignorance. People become sinners and lack virtue. They become slaves to their passions and are barely as powerful as their earliest ancestors in the Satya Yuga. Society falls into disuse and people become liars and hypocrites. Knowledge is lost and scriptures are diminished. Humans eat forbidden and dirty food. The environment is polluted, water and food become scarce. Wealth is heavily diminished. Families become non-existent. By the end of Kali Yuga the average lifespan of humans will be as low as 20 years.
Durations of the four Yugas
Relationship between various time units in Hindu cosmology
However, the actual duration of yugas is still controversial as in context of some text such as holy science written by Sri Yukteshwar Giri in which the true length of yugas is Mentioned to be as follows:
1. Satya yuga-4800
2. Treta yuga-3600
3. Dwarpa yuga-2400
Reminding,of miscalculation of 24,000 year cycle equivalent to devas years rather than human year
1 deva year= 365 Human years
Making, the now Concepted length of Yugas as follows:
1. Satya yuga= 4800×365= 1,752,000 years
2. Treta yuga= 3600×365= 1,314,000 years
3. Dwarpa yuga= 2400×365= 876,000 years
4. Kalyuga.=. 1200×365= 438,000 years
This calculation is also supported  by modern day spiritual masters such as Sadhguru Jaggi Vasudev.
According to one Puranic astronomical estimate, the four Yuga have the following durations:
- Satya Yuga equals 1,728,000 Human years
- Treta Yuga equals 1,296,000 Human years
- Dvapara Yuga equals 864,000 Human years
- Kali Yuga equals 432,000 Human years
Together, these four yuga constitute one Mahayuga, equal to 4.32 million human years. According to one version, there are 1,000 Mahayugas in one day of Brahma or 4.32 billion human years. A Mahakalpa consists of 100 years of Brahma.
According to Srimad Bhagavatam 3.11.19, which most scholars agree was composed around Mahabharat war(3000 to 3100 BC), the Yugas are much longer, using a divine year in which one day is equal to one human year, thus:
one year of the demigods is equal to 360 years of the human beings. The duration of the Satya-yuga is therefore 4,800 x 360, or 1,728,000 years. The duration of the Tretā-yuga is 3,600 x 360, or 1,296,000 years. The duration of the Dvāpara-yuga is 2,400 x 360, or 864,000 years.
The Viṣṇu Purāṇa Time measurement section of the Viṣṇu Purāṇa Book I Chapter III adds:
- 2 Ayanas (6-month periods, see above) = 1 human year or 1 day of the devas.
- 12,000 divine years = 4 Yugas (= 4,320,000 human years) = 1 Mahā-Yuga (also is equal to 12,000 Daiva (divine) Yuga).
- 2*12,000 = 24,000 divine year = 12000 revolutions of sun around its dual.
While the long yuga count is the most popular, it does not correlate to any known celestial motion found in the Astronomical Almanac. The value of 24,000 years fits relatively close with the modern astronomical calculation of one full precession of the equinox, which takes 25,772 years.[a] Thus the yuga cycle may have some basis in known terrestrial cycles. Srimad Bhagavatam 3.11.19 describes the timespans of the devas, in which a year of a yuga is a year of the demigods. It is this second sloka which appears to have been modified over the years.
The ages see a gradual decline of dharma, wisdom, knowledge, intellectual capability, life span, emotional and physical strength.
- Satya Yuga – Virtue reigns supreme. Human stature was 21 cubits. Average human lifespan was 100,000 years.
- Treta Yuga – There was 3 quarter virtue and 1 quarter sin. Normal human stature was 14 cubits. Average human lifespan was 10,000 years.
- Dwapara Yuga – There was 1 half virtue & 1 half sin. Normal human stature was 7 cubits. Average human lifespan was 1,000 years.
- Kali Yuga – There is 1 quarter virtue & 3 quarter sin. Normal human stature is 3.5 cubits. Average human lifespan will be 100 years.
In the present days we may be said to live in a Kali Yuga, which is said to have started in 3102 BCE with the end of the Mahabarata(Dwapra). This date is also considered by many Hindus to be the day that Lord Krishna left Earth and went to abode.[b]
- ^ This phenomenon is observed as the stars moving retrograde across the sky at about 50 arc seconds per year, and is thought to produce periods of warm ages and ice ages known as the Milankovitch cycle.
- ^ According to Sri Yukteswar Giri, guru of Paramahansa Yogananda, The ascending phase of the Kali Yuga began in September 499 CE (not exactly). Since September 1699, we have been in the ascending phase of the Dwapara Yuga. According to Sri yukteswar,since nobody wanted to announce the bad news of the beginning of the descending Kali Yuga, so they kept adding years to the Dvapara date (at that time 2400 Dvapara) only retitling the epoch to Kali.