Pohela Boishakh April 14

During Mughal rule, land taxes were collected from Bengalis according to the Islamic Hijri calendar. This calendar was a lunar calendar, and its new year did not coincide with solar agricultural cycles. According to some sources, the festival was a tradition introduced to Bengal during the reign of Mughal emperor Akbar to time the fiscal year to the harvest, and the Bangla year was thus called Bangabda. 

Akbar asked the royal astronomer Fathullah Shirazi to create a new calendar by combining the Islamic lunar calendar and the already used Hindu solar calendar, and this was known as Fasholi shan (harvest calendar). According to some historians, this started the Bengali calendar. According to Shamsuzzaman Khan, it may have been Nawab Murshid Quli Khan, a Mughal governor, who first used the tradition of Punyaho as "a day of ceremonial collection of land tax", and used Akbar's fiscal policy to start the Bengali calendar.

According to Shamsuzzaman Khan and Nitish Sengupta, the origin of the Bengali calendar is unclear. According to Shamsuzzaman, it is called Bangla shon or shaal, which are Arabic (سن) and Persian (سال) words respectively, suggesting that it was introduced by a Muslim king or sultan. "In contrast, according to Sengupta, its traditional name is Bangabda. It is also unclear whether it was adopted by Alauddin Husain Shah or Akbar. 

The tradition of using the Bengali calendar was perhaps started by Husain Shah before Akbar. Whoever adopted the Bengali calendar and the new year, Sengupta says, helped collect land taxes after the spring harvest based on the traditional Bengali calendar, because the Islamic Hijri calendar created administrative difficulties in fixing the date of collection.

Some historians attribute the Bengali calendar to the 7th century King Shashanka. The term Bangabda (Bangla year) is also found in two Shiva temples several centuries older than Akbar's era, suggesting that the Bengali calendar existed before Akbar's time. Various dynasties whose territories extended into Bengal, before the 13th century, used the Vikrami calendar. Buddhist texts and inscriptions created during the Empire period Pala mention "Vikrama" and months such as Ashvin, a system found in Sanskrit texts elsewhere in the ancient and medieval Indian subcontinent.

In rural Bengali communities of India, the Bengali calendar is credited as "Bikromaditto", like many other parts of India and Nepal. However, unlike those regions where it begins in 57 BCE, the Bengali calendar begins from 593 CE, suggesting that the starting base year was adjusted at some point.