New moon of Ashvin (Hindu calendar)
Deepavali which means "row of lights/lamps" in Kannada and Telugu and Marathi and Sanskrit is called "Diwali" in North India, Deepa means lamp and in Hindi a lamp is mostly called a Diya or Di. The festival is celebrated on the occasion of Lord Krishnaand his wife Satyabhama killing a demon Narakasura. Another story says the festival is celebrated for the return of Rama and Sita to the kingdom Ayodhya after fourteen years of exile.
Rama is exiled to the forest for 14 years, his devoted wife Sita and humble brother Laxman decide to join him, after 14 years the whole village know he is returning so light lamps or "divas" to guide him, his wife and brother home. So every year lamps are lit to represent Rama finding his way back home after the harsh punishment of being sent to exile in the forest.