The 5th ara is called Dushma Kaal. It is 21000 years long.
According to Jain philosophy, the Kaal chakra (wheel of time) changes continuously. Though the flow of Kaal Chakra is infinite, yet the wheel can be divided into six parts.
Just as the parts of the wheel of a car rotate from top to bottom and bottom to top, so these six parts of Kaal also continually change. The time when the world moves from happiness to sorrow and the knowledge of souls reduce gradually is called ‘Avsarpini Kaal’. While the time when the world moves from sorrow to happiness and the knowledge of souls increase gradually is called ‘Utsarpini Kaal’.
The total time of Avsarpini and Utsarpini Kaals is twenty kodakodi Sagaras (crores in crores Sagaras) which is called Kalpkaal. After uncountable Avsarpini Kaal comes a Hundapsarpini Kaal (so miserable time). Currently, it is the fifth Kaal of Hundapsarpini Kaal of which about 2535 years have been passed out of 21000 years and about 18465 years are remaining.
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P.S. : This is a part of an article translated by me for Vitragvani.