*The smallest unit of time is nimesha. This is the amount of time it takes to blink. Fifteen nimeshas make one kashtha and thirty kashthas are one kala. Thirty kalas make one muhurta and thirty muhurtas are one day. Thirty days are one month. Each month is divided into two lunar fortnights, shukapaksha and krishnapaksha. Six months are called an ayana. There are thus two ayanas in a year.*

Three hundred and sixty human years are equivalent to one year for the gods.

The lengths of the four yugas (eras) are defined in terms of years of the gods, not in terms of human years. There are four eras and their names are kritayuga or satyayuga, tretayuga, dvaparayuga and kaliyuga. Satyayuga lasts for four thousand divine years, tretayuga for three thousand, dvaparayuga for two thousand and kaliyuga for one thousand. This adds up to ten thousand divine years. The sandhyas and sandhyamshas are the intervening periods between the yugas and these add up to two thousand divine years. Thus, the four yugas taken together last for twelve thouand divine years.

In a kalpa (cycle), each of the four yugas occurs a thousand times. A kalpa has fourteen manvantaras (eras). In a manvantara, each of the four yugas thus occurs seventy one times. One kalpa corresponds to one day for Brahma. One thousand kalpas are one of Brahma's years and eight thousand of Brahma's years make one of Brahma's yugas. One thousand such yugas make up one savana and Brahma lives for three thousand savanas. This period is known as a trivrita.

During each of Vishnu's days, one Brahma is born and dies. And during each of Shiva's days, one Vishnu is born and dies.

Three hundred and sixty human years are equivalent to one year for the gods.

The lengths of the four yugas (eras) are defined in terms of years of the gods, not in terms of human years. There are four eras and their names are kritayuga or satyayuga, tretayuga, dvaparayuga and kaliyuga. Satyayuga lasts for four thousand divine years, tretayuga for three thousand, dvaparayuga for two thousand and kaliyuga for one thousand. This adds up to ten thousand divine years. The sandhyas and sandhyamshas are the intervening periods between the yugas and these add up to two thousand divine years. Thus, the four yugas taken together last for twelve thouand divine years.

In a kalpa (cycle), each of the four yugas occurs a thousand times. A kalpa has fourteen manvantaras (eras). In a manvantara, each of the four yugas thus occurs seventy one times. One kalpa corresponds to one day for Brahma. One thousand kalpas are one of Brahma's years and eight thousand of Brahma's years make one of Brahma's yugas. One thousand such yugas make up one savana and Brahma lives for three thousand savanas. This period is known as a trivrita.

During each of Vishnu's days, one Brahma is born and dies. And during each of Shiva's days, one Vishnu is born and dies.

- Shiva Purana