Digambar Jain tradition observes Diwali as the Mahavira Nirvana Day. The key point for Digambar timing is:

• Pujan date (Nirvana Day): Kartik Amavasya, with the Nirvana observance tied to that Amavasya night. In 2025, many Digambar sanghs mark this on Kartik Amavasya around October 20–21, with local calendars deciding the exact muhurat.

• If you are doing a dedicated puja that evening, timings vary by local panchang and temple notices. A common pattern is to perform prayers after sunset, as per the Amavasya night.

• Some local calendars may note a two-day Amavasya span (into October 21), but the main Jain Diwali day is usually October 20, 2025, for many sanghs; others might list October 21 depending on their calendar.

You can read more here and here .