The smallest cycle is called a maha yuga. A maha yuga is 4,320,000 human years. Each maha yuga is subdivided into the following four ages, whose lengths follow a ratio of 4:3:2:1:
Satya Yuga (also called Krita Yuga)
This first age is 1,728,000 human years. Also known as the Golden Age or age of Truth. The qualities of this age are: virtue reigns supreme; human stature is 21 cubits; lifespan is a lakh of years, and death occurs only when willed.
This second age is 1,296,000 human years. Also known as the Silver Age. The qualities of this age are: the climate is three quarters virtue and one quarter sin; human stature is 14 cubits; lifespan is 10,000 years.
This third age is 864,000 human years. Also known as the Bronze Age. The qualities of this age are: the climate is one half virtue and one half sin; lifespan is 1,000 years.
The fourth and last age is 432,000 human years. Also known as the Iron Age. This is the age in which we are presently living. The qualities of this age are: the climate is one quarter virtue and three quarters sin; human stature is 3.5 cubits; lifespan is 100 or 120 years. Within this maha yuga, we are in Kali Yuga. The 5100th year of Kali Yuga will correspond to the year 2,000 A.D. That means that we are fairly early in Kali Yuga and this age will continue 426,000 more years.