The culture of Kerala is composite and cosmopolitan in nature and it is an integral part of Indian culture.[28] It is a synthesis of Aryan, Dravidian, Arab, and European cultures,[29] developed over millennia, under influences from other parts of India and abroad.[30] It is defined by its antiquity and the organic continuity sustained by the Malayali people.[31] It was elaborated through centuries of contact with neighbouring and overseas cultures.[32] However, the geographical insularity of Kerala from the rest of the country has resulted in the development of a distinctive lifestyle, art, architecture, language, literature and social institutions.[28] Over 10,000 festivals are celebrated in the state every year.[6] The Malayalam calendar, a solar sidereal calendar started from 825 CE in Kerala,[34] finds common usage in planning agricultural and religious activities.[35] Malayalam, one of the classical languages in India, is Kerala's official language.[36] Over a dozen other scheduled and unscheduled languages are also spoken.[37] Kerala has the greatest consumption of alcohol in India.[38]