Answer

Shwetambar Jain chaumas 2026 starts on Tuesday, 28 July 2026 — Ashadh Sud 14 / Chaumasi Chaudas — in the Jain calendar listings and Shwetambar community calendars I found. ( drikpanchang.com)

Explanation

In Shwetambar observance, this day is marked as Chaturmas Prarambh or Chaumasi Chaudas. Because Jain dates follow the local panchang, there can sometimes be a small regional variation in observance. ( drikpanchang.com)

Takeaway

For 2026, the practical start date to note is 28 July 2026. ( drikpanchang.com)