section_path: History/Buddhist/Hindu influence
section_name: Hindu influence
paragraph_text: Hindu influence
  
  Some historians attribute the Bengali calendar to the 7th century Bengali king Shashanka, whose reign covered the Bengali era of 594 CE. The term Bangabda (Bangla year) is found too in two Shiva temples many centuries older than Akbar era, suggesting that a Bengali calendar existed long before Akbar's time.
  
  Hindus developed a calendar system in ancient times. Jyotisha, one of the six ancient Vedangas, was the Vedic era field of tracking and predicting the movements of astronomical bodies in order to keep time. The ancient Indian culture developed a sophisticated time keeping methodology and calendars for Vedic rituals.
  
  The Hindu Vikrami calendar is named after king Vikramaditya and starts in 57 BCE. In rural Bengali communities of India, the Bengali calendar is credited to "Bikromaditto", like many other parts of India and Nepal. However, unlike these regions where it starts in 57 BCE, the Bengali calendar starts from 593 suggesting that the starting reference year was adjusted at some point.
  
  Various dynasties whose territories extended into Bengal, prior to the early 13th-century, used the Vikrami calendar. For example, Buddhist texts and inscriptions created in the Pala Empire era mention "Vikrama" and the months such as Ashvin, a system found in Sanskrit texts elsewhere in ancient and medieval Indian subcontinent.
  
  Hindu scholars attempted to keep time by observing and calculating the cycles of the Sun (Surya), Moon, and the planets. These calculations about the Sun appear in various Sanskrit astronomical texts in Sanskrit, such as the 5th century Aryabhatiya by Aryabhata, the 6th century Romaka by Latadeva and Panca Siddhantika by Varahamihira, the 7th century Khandakhadyaka by Brahmagupta and the 8th century Sisyadhivrddida by Lalla. These texts present Surya and various planets and estimate the characteristics of the respective planetary motion. Other texts such as Surya Siddhanta dated to have been complete sometime between the 5th century and 10th century.
  
  The current Bengali calendar in use by Bengali people in the Indian states such as West Bengal, Tripura, Assam, and Jharkhand is based on the Sanskrit text Surya Siddhanta and includes the modifications introduced during the reign of Shashanka, the first independent ruler of Gauda. The timeline Shashanka becoming the sovereign ruler of Bengal rising from a territorial ruler matches with the first year of Bangabda. It retains the historic Sanskrit names of the months, with the first month as Baishakh. Their calendar remains tied to the Hindu calendar system and is used to set the various Bengali Hindu festivals.