Answer

Magshar Vad Dasham means the 10th tithi of the dark half of the Jain/Hindu lunar month of Magshar.

In the commonly followed Gujarati/Jain calendar, it usually falls around November–December in the English calendar.

Explanation

• Magshar = the lunar month after Kartak
• Vad = dark fortnight, after Poonam and before Amas
• Dasham = 10th lunar day

The exact English date changes every year because it depends on the lunar calendar and local sunrise-based tithi calculation.

Takeaway

To know the exact date for a particular year, you should check a Jain Panchang for your location.