The Bengali Panjika and Bangabda: Months from Sankrantis, and Why Bangladesh and West Bengal Differ

The Bengali year runs by the Sun, not the Moon. It begins when the Sun enters sidereal Aries, and each time the Sun changes sign a new month begins. The moment of the change is called sankranti; the day after Chaitra Sankranti is Pohela Boishakh, the new year.

Months and signs

These are approximate dates in the traditional, sankranti-based reckoning. Because the earth's orbit is elliptical the Sun does not spend equal time in each sign: it moves slowly in summer and fast in winter, so in the traditional almanac Jyoishtho and Asharh run 31 or 32 days and Poush and Magh 29 or 30.

Which day is the sankranti?

The sankranti moment can fall at any hour. By the usual Bengali rule, if it falls before midnight the next day is the first of the new month; if after midnight, the day after that. This rule shifts the start of a month by a day either way, and almanacs sometimes disagree slightly.

Why Bangladesh and West Bengal differ

In 1987 Bangladesh adopted a fixed calendar on the Bangla Academy's recommendation, revised again in 2019. Under the current rules:

• Pohela Boishakh is always 14 April.
• The first six months, Boishakh to Ashwin, have 31 days.
• Kartik to Choitro have 30 days, except Falgun with 29 (30 in a leap year).
• So 21 February is always 8 Falgun, 16 December always 1 Poush and 26 March always 12 Choitro.

Bengalis in West Bengal, Tripura and Assam still follow the traditional Surya Siddhanta or modern calculated almanacs, where months start at the actual sankranti. There Pohela Boishakh falls on 14 or 15 April, and other dates can differ from Bangladesh by a day or two.

Religious tithis and nakshatras do not differ at all; only the numbering of Bengali dates does.

Counting the Bangabda year

From Pohela Boishakh to 31 December, subtract 593 from the Common Era year; from 1 January to the end of Choitro, subtract 594. Bangabda 1433 began on 14 April 2026 and runs to 13 April 2027.

Two accounts of its origin are common. One credits the Mughal emperor Akbar, whose administration converted the lunar Hijri year to a solar "fasli" year for collecting land revenue. The other traces it to King Shashanka of Gauda. Historians still debate the question.

The lunar months are kept too

The Bengali panjika also tracks lunar months, since most festivals follow tithis: Durga Puja in the bright half of Ashwin, Kali Puja on the Amavasya of Kartik, Dol on the full moon of Falgun. A lunar year is about 11 days shorter than a solar one, so roughly every three years an extra month (mala masa or adhika masa) is added to keep festivals in their seasons.

Suvolagna's daily panchang shows the Bangabda date, tithi and sankranti every day.