A mahā-kalpa (Skt. mahākalpa; Tib. བསྐལ་ཆེན་, Wyl. bskal chen) is equal to 300,000 saras and one sara is the time required to exhaust the sands of the seven Ganges (each Ganges being 500 yojanas or 2250 miles in length, 2¼ miles in breadth, and 50 dhanus or 100 yards in depth), at the rate of putting 100 years for the removal of one grain of sand.
Traditionally, it is said that there are four kalpas: formation, existence, destruction and emptiness (each portion is called asamkhyeya-kalpa). All four together are the lifespan of a world, and collectively are a complete cycle, called mahakalpa. Each of the four principle kalpas is subdivided into twenty antara-kalpas, or "small kalpas." There are different distinctions and illustrations of kalpas. In general, a small kalpa is represented as 16,800,000 years, a kalpa as 336,000,000 years and a maha-kalpa is 1,334,000,000 years. Yet, these numbers are symbolic, not literal.
"Truthfully, the quantities of years assigned to a Cosmic Day are symbolic. The Cosmic Night arrives when the in gathering of the perfect souls is complete, which means, when the Cosmic Day is absolutely perfected."