Answer in brief: Digambar Jains, like Śvetāmbara Jains, honor Mahavira’s Nirvana on Diwali. The puja is best performed on Kartik Amavasya night, after sunset, with lamps lit and prayers. Many observe during the Pradosh Kaal or the Nishita (midnight) muhurat, and continue a period of reflection, vow-keeping, and simple living.
Why this time: Diwali marks the Nirvana of Mahavira (and the following day Gautam Swami’s keval jnana in some traditions). The emphasis is on awakening knowledge, renunciation, and ahimsa, so the evening/night hours are considered especially auspicious for devotional puja and contemplation. While the exact ritual times can vary a bit between Digambar and Śvetāmbara communities, the general practice centers on Kartik Amavasya night and lamps as a sign of spiritual light. ( jainknowledge.com)
Date note for 2025: Kartik Amavasya falls on October 20, 2025, with the Amavasya tithi running into October 21. Diwali puja is typically observed on that Amavasya night. ( timesofindia.indiatimes.com)