Diwali marks the triumph of good over evil. According to Hindu mythology, Hindu God Rama returned from a 14-year exile and defeated the evil god Ravana. During his exile, it said the people were in a dark place.
Upon his return, people prepared and started spring cleaning, the dawn of a new beginning, lighting lamps, fires, and candles. The festival of light as it became to celebrate the goodness of light overcoming the evil of darkness.
Sikhs celebrate the 1619 release of their 6th Guru Hargobind at Diwali
Jains celebrate the 24th Tirthankar Bhagwan Mahaveer attained Liberation at Pawapur / Bihar 2500 yrs ago on Diwali.