Diwali - also known as the Festival of Lights - is one of the major festivals in Hinduism, Sikhism, Jainism and Buddhism. The festival is celebrated annually. The central theme of the festival is the triumph of light over darkness or good over evil. This year, Diwali will be celebrated tomorrow. In many regions of India, Diwali is celebrated over five days. The date selected on the Gregorian calendar is based on the Hindu calendar.