Age of Brahmā
From Theosopedia
In Hinduism, world periods are measured in terms of days and nights of Brahmā, kalpas and yugas.
A day of Brahmā or a kalpa is equivalent to 4,320,000,000 years, while a night of Brahmā is of equivalent duration. Thus a day and night totals 8,640,000,000 years. A year of Brahmā then is 3,110,400,000,000 years, and 100 such years is the Age of Brahmā, which is 311,040,000,000,000 years. This is the mahā-manvantara, or age of manifestation, to be followed by mahā-pralaya or period of non-manifestation. See also YUGA.