It is since ancient times that Diwali has been celebrated. Now it is not easy to say what really was the reason behind its origin. Different people believe different events to be the cause behind this festival. In north India people believe Diwali is celebrated when Rama comes back from Exile with his wife Sita after slaying Ravana in an epic battle and people in south India believe on this day Sri Krishna killed the demon king Narakasura with his wife Sathyabama. But mainly Diwali is celebrated for the victory of good over evil.

On the Occasion of Diwali (2015), let me share a video, which was screened during Diwali Night 2011 at the Reynolds Performing arts center, The University of Oklahoma, Norman, this video tells the story of Rama. 

Diwali (or Deepavali, the "festival of lights") is an ancient Hindu festival celebrated every year. Diwali is one of the largest and brightest festivals in India. The festival spiritually signifies the victory of light over darkness, knowledge over ignorance, good over evil, and hope over despair. Its celebration includes millions of lights shining on housetops, outside doors and windows, around temples and other buildings in the communities and countries where it is observed. The festival preparations and rituals typically extend over a five day period, but the main festival night of Diwali coincides with the darkest, new moon night of the Hindu Lunisolar month Kartika. In the Gregorian calendar, Diwali night falls between mid-October and mid-November.

Before Diwali night, people clean, renovate, and decorate their homes and offices. On Diwali night, Hindus dress up in new clothes or their best outfit, light up diyas (lamps and candles) inside and outside their home, participate in family puja (prayers) typically to Lakshmi – the goddess of wealth and prosperity. After puja, fireworks follow, then a family feast including mithai (sweets), and an exchange of gifts between family members and close friends. Deepavali also marks a major shopping period in nations where it is celebrated.

Diwali is an important festival for Hindus. The name of festive days as well as the rituals of Diwali vary significantly among Hindus, based on the region of India. In many parts of India, the festivities start with Dhanteras (in Northern and Western part of India), followed by Naraka Chaturdasi on second day, Deepavali on the third day, Diwali Padva dedicated to wife–husband relationship on the fourth day, and festivities end with Bhau-beej dedicated to sister–brother bond on the fifth day. Dhanteras usually falls eighteen days after Dussehra.

On the same night that Hindus celebrate Diwali, Jains celebrate a festival of lights to mark the attainment ofmoksha by Mahavira, Sikhs celebrate Bandi Chhor Divas and some Buddhists also celebrate Diwali remembering Ashoka's conversion to Buddhism. Diwali is an official holiday in Nepal, India, Sri Lanka,Mauritius, Guyana, Trinidad and Tobago, Suriname, Malaysia, Singapore and Fiji.