For the year 2026 (based on the Indian lunar calendar):

• Chaturmās begins:

Saturday, 25 July 2026 – Āṣāḍh Shukla Ekādashī (Devśayanī Ekādashī) – from this tithi Jain Chaturmās starts.

• Chaturmās ends:

Friday, 20 November 2026 – Kārtik Shukla Ekādashī (Devuthānī / Prabodhinī Ekādashī) – on this tithi Chaturmās is completed.

Note: Some Jain saṅghs/derāsars consider the more formal “pakkā chaturmās” to begin from Āṣāḍh Sud Chaudash (around 28 July 2026, depending on place and panchāng), so exact observance can vary slightly by city and by tradition.