Duration of Yugas

According to the Laws of Manu, one of the earliest known texts describing the yugas, the length is 4800 years + 3600 years + 2400 years + 1200 years for a total of 12,000 years for one arc, or 24,000 years to complete the cycle (one precession of the equinox). There is no mention of a year of the demigods or any years longer than the solar, which is consistent with description in The Holy Science. However, the one debatable interpretation from the Srimad Bhagavatam states the following: "The duration of the Satya millennium equals 4,800 years of the demigods; the duration of the Dvāpara millennium equals 2,400 years; and that of the Kali millennium is 1,200 years of the demigods... As aforementioned, 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. And the last, the Kali-yuga, is 1,200 x 360, or 432,000 years in total." (Śrīmad Bhāgavatam 3.11.19) . These 4 yugas follow a timeline ratio of (4:3:2:1).

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 & 1 quarter sin. Normal human stature was 14 cubits. Average human lifespan was 10,000 years.

Dwapar Yuga: – There was 1 half virtue & 1 half sin. Normal human stature was 7 cubits. Average human lifespan was 1000 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. Towards the end of the Yuga this will come down to 20 years.