For Jains, Chaumasa (Chaturmās) starts from Āshādh Shukla Ekādashi (Devshayanī / Āshādhī Ekādashi).

For the year you likely mean – 2026 (not 2926) – most reliable panchāngs place:

• Chaumasa start (Āshādh Shukla Ekādashi):

Please note:

• Some Jain saṅghs do the main “Chaturmās Prārambh” program on Āshādh Sud Chaudas (14), which will be just a couple of days after this date in 2026, so you may also see a local announcement around 27–28 July 2026.
• Exact observance can shift by one day depending on your city and the panchāng your derāsar follows, so always confirm with your local Jain calendar or temple notice.

You can read a simple explanation of when Chaumasa starts and ends here