A commentator on the Amazon World History Timeline at All Girl Worlds writes the following:

The yugas or ages are concepts of Vedic knowledge. The yuga’s first introduction is in the Mahabharata. According to Vedic knowledge the duration of each yuga is: Satya-yuga 1,728,000 years, Treta-yuga 1,296,000 years, Dvapara-yuga 884,000 years, Kali-yuga 432,000 years. The Vedic knowledge states that in the Satya-yuga there is neither hate, envy, fear, nor care. That there is only one God, one Veda, one law, and one ritual. The following yugas are a decay of this golden yuga.

To which the editors reply as follows:

Thank you for your information. It is indeed correct. The Yugas are indeed found in the Vedas, while the Four Ages (Gold, Silver, Bronze and Iron) are found independently in the Hellenic tradition and the same idea is found in many other traditions throughout the world, including the Hebrew, Mayan and Inca. As you correctly state, the movement of the four Ages is one of decline and decay. As to the length of the Cycle or Manvantara, one must realize that there are cycles within, cycles, from the great Cycle of Manifestation itself (ie the "lifetime of the universe") to a single in/out breath of any given being. The cycle of most relevance to the history of the current humanity is of about 60,000 years, though certainly this is only one sub-cycle within the greater cycle you mention (which itself is a sub-cycle of yet greater cycles). For more information on cycles in the primordial feminine tradition, please see the following