Mahavir Day (Mahavir Jayanti) does not fall on a fixed weekday. In Jain tradition, it is observed on the 13th day of the bright half (Shukla Paksha) of the month of Chaitra in the Jain lunar calendar. Because this tithi shifts with the lunar calendar, the weekday changes each year. For example, in 2025 the festival fell on Thursday, April 10, based on Chaitra Shukla Trayodashi. ( timesofindia.indiatimes.com)

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