Answer

Gautam Swami attained Keval Gyan on the day of Diwali, after Bhagwan Mahavir attained Nirvana.

Explanation

According to Jain tradition, Gautam Swami had deep attachment and devotion toward Bhagwan Mahavir. When Bhagwan Mahavir attained Nirvana at Pavapuri on Diwali, Gautam Swami overcame his final inner attachment and attained Keval Gyan.

Takeaway

Diwali is therefore spiritually significant in Jain Dharma not only as the day of Bhagwan Mahavir’s Nirvana, but also as the day Gautam Swami attained Keval Gyan.