Diwali or Deepavali is the Hindu festival of lights celebrated every year in autumn in the northern hemisphere (spring in southern hemisphere). It is an official holiday in Fiji, Guyana, India, Malaysia, Mauritius, Myanmar, Nepal, Singapore, Sri Lanka, Suriname, Trinidad and Tobago. One of the most popular festivals of Hinduism, it spiritually signifies the victory of light over darkness, good over evil, knowledge over ignorance, 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 dark night of the Hindu Lunisolar month Kartika in Bikram Sambat calendar (the month of Aippasi in Tamil Calendar), on the 15th of the month. In the Gregorian calendar, Diwali night falls between mid-October and mid-November.