Boishakh 2020
During the Mughal rule, land taxes were collected from Bengali people according to the Islamic Hijri calendar. This calendar was a lunar calendar, and its new year did not coincide with the solar agricultural cycles. According to some sources, the festival was a tradition introduced in Bengal during the rule of Mughal Emperor Akbar to time the tax year to the harvest, and the Bangla year was therewith called Bangabda. Akbar asked the royal astronomer Fathullah Shirazi to create a new calendar by combining the lunar Islamic calendar and solar Hindu calendar already in use, and this was known as Fawsholi shawn (harvest calendar). According to some historians, this started the Bengali calendar. According to the Bangladeshi academic and foklorist Shamsuzzaman Khan, it could be Nawab Murshid Quli Khan, a Mughal governor, who first used the tradition of Punyaho as "a day for ceremonial land tax collection", and used Akbar's fiscal policy to start the Bangla calendar.
According to Shamsuzzaman Khan, and Nitish Sengupta, the origin of the Bengali calendar is unclear. According to Shamsuzzaman, "it is called Bangla shawn or shaal, which are Arabic and Parsian words respectively, suggests that it was introduced by a Muslim king or sultan."[10] In contrast, according to Sengupta, its traditional name is Bangabda.
Some historians attribute the Bengali calendar to the 7th century king Shashanka. The term Bangabda (Bangla year) is found too in two Shiva temples many centuries older than Akbar era, suggesting that Bengali calendar existed before Akbar's time. It is also unclear, whether it was adopted by Hussain Shah or Akbar. The tradition to use the Bengali calendar may have been started by Hussain Shah before Akbar. Regardless of who adopted the Bengali calendar and the new year, states Sengupta, it helped collect land taxes after the spring harvest based on traditional Bengali calendar, because the Islamic Hijri calendar created administrative difficulties in setting the collection date.
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 CE suggesting that the starting reference year was adjusted at some point.