Thai culture and traditions incorporate a great deal of influence from India, China, Cambodia, and the rest of Southeast Asia. Thailand's national religion, Theravada Buddhism, is central to modern Thai identity. Thai Buddhism has evolved over time to include many regional beliefs originating from Hinduism, animism, as well as ancestor worship. The official calendar in Thailand is based on the Eastern version of the Buddhist Era (BE). Thai identity today is a social construct of Phibun regime in 1940s.