In April, we celebrate a festival of Bangladeshis, on 14th April. In our country, Bangla or bangladesh is a form of Islamic hijri. The original Hijri calendar is dependent on lunar month.
In the time of Mughal Emperor Akbar in India, it was decided to convert the existing Hijri Chandra Panjika into solar panels. Samrat Akbar gave the responsibility of converting Hijri lunar calendar to solar calendar by eminent scientist and astronomer, Amir Fathullah Siraji.
For this, the counting of Bangaad started from 963 AH. Earlier the month of Chakraborty or Shaka in the first month of Bengal was the month of Chaitra. But the month of Muharram in 963 AH was the Bengali month of Baishakh, that is why the Baishakh month is the first month of Bangad or Bangla calendar and 1st Baishakh is considered the New Year.
If the Bangla version is mainly Hijri. From the migration of the Prophet (pbuh) to the beginning of this calendar. 1415 BC means 1415 years after the hijrah of the Prophet (peace be upon him). 962 lunar years and the next 453 years of solar year. The solar year is 11/12 days more than the lunar year and the lunar year is increased for one year every 30 years.For this, Bengal is 1318-19 years, according to 1433 AH.