According to Jain cosmology, time is divided into endless cycles, each with two halves: Utsarpini (ascending, progressive era) and Avasarpini (descending, degenerative era). We are currently in the Avasarpini era.

Each half-cycle (Utsarpini or Avasarpini) is divided into six unequal periods (aras), and each full cycle is extremely long, lasting billions of years.

When will Avasarpini end and the next Utsarpini start? According to Jain scriptures, we are presently in the fifth ara (duḥṣamā) of Avasarpini. After this, there will be a sixth and final ara (duḥṣamā-duḥṣamā), which is even more degenerate. When this sixth ara ends, the current Avasarpini will be over, and a new Utsarpini will begin.

Exact timing: Jain texts specify the duration of each ara, but the numbers are astronomically large. For example, in Bharat Kshetra (where we live), the total duration of Avasarpini is said to be 10 crore crore (100 trillion) Sagaropama years, and each Sagaropama is itself of unimaginable length (one Sagaropama is the time taken to empty a well 1 yojan × 1 yojan × 1 yojan, by taking out one drop every 100 years).

In summary:

• We are in the fifth ara of Avasarpini.
• After the sixth ara, this Avasarpini will end, and Utsarpini will start.
• The exact time left is extremely vast—many millions of years according to Jain scriptures.

References:

• Tattvartha Sutra (Jain canonical text)
• Jain Cosmology by Dr. Colette Caillat and Acharya Mahaprajna

If you want to know the detailed calculation or the duration of each ara, please let me know!