The Bengali Calendar or Bangla Calendar (Bengali: বঙ্গাব্দ, lit. ‘Baṅgābda’), colloquially (Bengali: বাংলা সন, romanized: Baṅgla Śon), is a luni-solar calendar used in the Bengal region of the Indian subcontinent. A revised version of the calendar is the national and official calendar in Bangladesh and an earlier version of the calendar is followed in the Indian states of West Bengal, Tripura and Assam. The New Year in the Bengali calendar is known as Pohela Boishakh.
The Bengali era is called Bengali Sambat (BS) or the Bengali year (বাংলা সন Bangla Sôn, বাংলা সাল Bangla sal, or Bangabda) has a zero year that starts in 593/594 CE. It is 594 less than the AD or CE year in the Gregorian calendar if it is before Pôhela Bôishakh, or 593 less if after Pôhela Bôishakh.
The revised version of the Bengali calendar was officially adopted in Bangladesh in 1987. Among the Bengali community in India, the traditional Indian Hindu calendar continues to be in use, and it sets the Hindu festivals .
All of data’s collected from Wikipedia.