Pohela Boishakh (Bengali: পহেলা বৈশাখ, or Bengali New Year Bengali: বাংলা নববর্ষ, Bangla Nôbobôrsho), occurring on 14 April or 15 April, is the first day of the Bengali calendar, celebrated in the Bangladesh and in the Indian state of West Bengal, by the Bengali people and also by minor Bengali communities in other Indian states, including Assam, Tripura, Jharkhand and Orrisa. It coincides with the New Year's days of numerous Southern Asian calendars. The traditional greeting for Bengali New Year is শুভ নববর্ষ "Shubhô Nôbobôrsho".
The Bengali calendar is loosely tied with the Hindu Vedic solar calendar, based on the Surya Siddhanta. As with many other variants of the Hindu solar calendar, the Bengali calendar commences in mid-April of the Gregorian year. The first day of the Bengali year therefore coincides with the mid-April new year in Mithila, Assam, Burma, Cambodia, Kerala, Manipur, Nepal, Odisha, Sri Lanka, Tamil Nadu and Thailand. Origin of Bongabdo or Bangla Year is debated with primarily two hypothesis but historicity of none could be proved till date. The development of the Bengali calendar is often attributed to king of Gour or Gauda, Shashanka as the starting date falls squarely within his reign. Mughal Emperor Jalaluddin Muhammad Akbar, the renowned grandson of Zahiruddin Muhammad Babur, the 3rd Mughal Emperor, introduced the Bengali Calendar. For relatively easier tax collection, Akbar changed the practice of agricultural tax collection according to the Hijri calendar. He ordered an improvement because the Hijri calendar, being lunar, did not agree with the harvest sessions and eventually the farmers faced severe difficulties in paying taxes out of season. The regal astrologer of Emperor Akbar's reign, Aamir Fatehullah Siraji, developed this calendar, after researching the lunar Hijri and solar calendars. The distinctive characteristic of the Bengali year was that, rather than being a lunar calendar, it was based on a union of the solar and lunar year. This was essentially a great promotion, as the solar and lunar years were formulated in very diverse systems. Primarily this calendar was named as “Fasli San” and then Bongabdo or Bangla Year was launched on 10/11 March 1584, but was dated from 5 November 1556 or 963 Hijri. This was the day that Akbar defeated Himu in the clash of Panipat 2 to ascend the throne. Akbar-e-Azam’s ordered to resolve all dues on the last day of Choitro. The next day was the first day of the New Year (Bengali New Year), the day for a new opening; landlords used to allocate sweets among their tenants, and businessmen would commence a “Halkhata” (new financial records book) and lock their old ones. Vendors used to provoke their consumers to allocate sweets and renew their business relationship with them. There were fairs and festivities allover and gradually Poila Boishakh became a day of celebration. The Bengali New Year begins at dawn, and the day is marked with singing, processions, and fairs. Traditionally, businesses start this day with a new ledger, clearing out the old. People of Bangladesh enjoy a national holiday on Poila Boishakh. All over the country people can enjoy fairs and festivals. Singers perform traditional songs welcoming the new year. Vendors sell conventional foods and artisans sell traditional handicrafts. People enjoy traditional jatra plays. Village dwellers of Bangladesh traditionally clean their house and people usually dress up in new clothes. Like other festivals of the region, the day is marked by visiting relatives, friends and neighbors. People prepare special dishes for their guests. The rural festivities have now evolved to become vast events in the cities, especially the capital Dhaka. In Dhaka and other large cities, the festivals begin with people gathering under a big tree. People also find any bank of a lake or river to witness the sunrise. Artists present songs to welcome the new year, particularly with Rabindranath Tagore's well-known song "Esho, he Boishakh". People from all spheres of life wear traditional Bengali dresses. Women wear traditional saris with their hair bedecked in flowers. Likewise, men prefer to wear traditional panjabis. A huge part of the festivities in the capital is a vivid procession organized by the students and teachers of Institute of Fine Arts, University of Dhaka. Nowadays, Poila Boishakh celebrations also observe a day of cultural unity without distinction between class, race and religious affiliations. Of the major holidays celebrated in Bangladesh and West Bengal, only Pôila Boishakh comes without any preexisting expectations. Unlike Eid ul-Fitr and Durga Pujo, where dressing up in lavish clothes has become a norm, or Christmas where exchanging gifts has become an essential part of the holiday, Pôila Boishakh is about celebrating the simpler, rural roots of the Bengal. Eventually, more people can take part in the festivities without the load of having to reveal one's class, religion, or finances.