Kalpa is said to be a great day of Lord Brahma. The simplest calculation of a Kalpa is its being one thousand great ages or ages of the gods. Thus 4,320,000 years or a divine age, multiplied by thousand is equal to 4,320,000,000 years. This is a day or night of Lord Brahma.

In the Hindu mythology it is believed that one year of mortals is equal to one day of the gods. Twelve thousand divine years are equal a period of four Yugas. The Krita Yuga has its mornings and evenings for four thousand and eight hundred years. Another Yuga is that Treta Yuga is the age with its mornings and evenings of about three thousand and six hundred celestial years. Dvapara Yuga is the age with two thousand and four hundred divine years. The last age is the Kali Yuga which consists of one thousand and two hundred divine years.

One day of the gods is equal to one year of mortals. Thus, the twelve thousand divine years must be multiplied by three hundred and sixty, the assumed number of days in a year, gives the number of the years of mortals in this great period of four yugas. Hence 4,320,000,000 human years is equal to one day of Brahma and his night is of the same duration.

Within this period of a day of Brahma, fourteen Manus reigns so formed the Manwantara. The fourteen Manus are equal to the fourteenth part of a day of Brahma.

In the present Kalpa or a day of Brahma, six manus are formed. Swayambhuva was the first Manu of the Manwantara which have been already passed away. The present Manu is Vaivaswata. In each Manwantara seven Rishis, certain deities, an Indra, a Manu, and the kings, his sons, are created and perish. A thousand of the systems of four Yugas occur coincidently with these fourteen Manwantaras. As a result about seventy one systems of four Yugas elapse during each Manwantara, and measure the lives of the Manu and the deities of the period.

At the close of this day of Brahma, the universe will be destroyed which will last through a night of Brahma equal in duration to his day. During the destruction of the universe, the three worlds, Sarga, Martha and Patal will be converted into one great ocean. When the universe will be destroyed then the lotus born God, Brahma will awake from his sleep and create a new universe.