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The Bengali calendar (Bengali: বঙ্গাব্দ Bônggabdo or বাংলা সন Bangla Shôn) or Bangla calendar is a traditional solar calendar used in Bangladesh and India's eastern states of West Bengal, Assam and Tripura. The year begins on Pôhela Baishakh, which falls on 14 April in Bangladesh and 15 April in India. In Assam, this corresponds to Bhaskar Era, named after the Kamarupa king, Bhaskara Varman.

The current Bengali year is 1416. The Bengali year is always 593 less than the year in the Gregorian calendar of the Christian Era or Anno Domini era or Common Era or Current Era for the period after Pôhela Boishakh. However, the Bengali year is 594 less than the Gregorian year if it is before Pôhela Boishakh.



King Shashanka of Ancient Bengal, who ruled approximately between 590 AD and 625 AD, is credited with starting the Bengali era[1]. Shashanka was the sovereign king of Bengal at the start of seventh century. Much of today’s Indian states of Bengal, Bihar, and Orissa was under his kingdom. The starting point of the Bengali era is estimated to be on Monday, 12 April 594 in Julian Calendar and Monday, 14 April 594 in the proleptic Gregorian calendar. The Bengali calendar is derived from the Hindu solar calendar, which is itself based on the Surya Siddhanta.

Mughal Emperor Akbar, who ruled from 1556 AD until 1605 AD, and one of his councillor Fatehullah Shirazi are credited with modifying the new Bengali calendar for tax collection purposes. Before the introduction of the Bengali calendar, during Muslim rule in India agricultural and land taxes were collected according to the Islamic Hijri calendar. However, as the Hijri Calendar is a lunar calendar, the agricultural year did not always coincide with the fiscal year. Therefore, farmers were hard-pressed to pay taxes out of season. In order to streamline tax collection, Emperor Akbar ordered a reform of the calendar. Accordingly, Amir Fatehullah Shirazi, a renowned scholar of the time and the royal astronomer, formulated a new calendar based on the lunar Hijri and solar Hindu calendars. The resulting Bangla calendar was introduced following the harvesting season when the peasantry would be in a relatively sound financial position. In keeping with the harvesting season, this new calendar initially came to be known as the Harvest Calendar, or ফসলী সন Fôsholi Shôn. During the reign of the Mughals, the Bengali Calendar was officially implemented throughout the empire. The name of the months continued to be in Sanskrit. Akbar did not start the Bengali calendar with a value 0, but instead jump-started it with the then existing hijri-calendar value.[2]


বঙ্গাব্দ Bônggabdo
Bengali Calendar
মাস Mash
কাল/ঋতু Kal/Ritu
বৈশাখ Boishakh
গ্রীষ্ম Grishsho
জ্যৈষ্ঠ Joishţho
আষাঢ় Ashaŗh
বর্ষা Bôrsha
Rainy (Monsoon)
শ্রাবণ Srabon
ভাদ্র Bhadro
শরৎ Shôrot
আশ্বিন Ashshin
কার্তিক Kartik
হেমন্ত Hemonto
অগ্রহায়ণ Ôgrohaeon
পৌষ Poush
শীত Šit
মাঘ Magh
ফাল্গুন Falgun
বসন্ত Bôshonto
চৈত্র Choitro


The Bengali calendar consists of 6 seasons, with two months comprising each season. Beginning from Pohela Boishakh, they are Grishsho (গ্রীষ্ম) or Summer; Bôrsha (বর্ষা) or Rainy/Monsoon season; Shôrot (শরৎ) or Autumn; Hemonto (হেমন্ত) or the Dry season; Šit (শীত) or Winter; and Bôshonto (বসন্ত) or Spring.


The names of the twelve months of the Bengali calendar are based on the names of the নক্ষত্র nokkhotro (lunar mansions): locations of the moon with respect to particular stars during the lunar cycle. These names were derived from the Surya Siddhanta, an ancient Indian book on Astronomy. The names of the months are:

  • বৈশাখ Boishakh after the star, বিশাখা Bishakha (Librae)
  • জ্যৈষ্ঠ Joishţho after the star, জ্যেষ্ঠা Jeshţha (Scorpius)
  • আষাঢ় Ashaŗh after the star, উত্তরাষাঢ়া Uttorashaŗha (Sagittarii)
  • শ্রাবণ Srabon after the star, শ্রবণা Srobona (Aquilae)
  • ভাদ্র Bhadro after the star, পূর্বভাদ্রপদ Purbobhadropôd (Pegasus and Andromeda)
  • আশ্বিন Ashshin after the star, অশ্বিনী Ôshshini (Arietis)
  • কার্তিক Kartik after the star, কৃত্তিকা Krittika (Pleiades)
  • অগ্রহায়ণ(মার্গশীর্ষ) Ôgrohaeon after the star, মৃগশিরা Mrigoshira
  • পৌষ Poush after the star, পুষ্যা Pushsha (Cancer)
  • মাঘ Magh after the star মঘা Môgha (Regulus)
  • ফাল্গুন Falgun after the star, উত্তরফাল্গুনী Uttorfalguni (Leonis and Denebola), and
  • চৈত্র Choitro after the star, চিত্রা Chitra (Spica)

Names and approximate lengths of Bengali months :[3]

No. Name Bengali Days
1 Boishakh বৈশাখ 30 / 31
2 Joishtho জ্যৈষ্ঠ 31 / 32
3 Asharh আষাঢ় 31 / 32
4 Srabon শ্রাবণ 31 / 32
5 Bhadro ভাদ্র 31 / 32
6 Ashshin আশ্বিন 30 / 31
7 Kartik কার্তিক 29 / 30
8 Ogrohayon অগ্রহায়ণ 29 / 30
9 Poush পৌষ 29 / 30
10 Magh মাঘ 29 / 30
11 Falgun ফাল্গুন 29 / 30
12 Choitro চৈত্র 30 / 31


The Bengali Calendar incorporates the seven-day week as used by many other calendars. Also like other calendars, the names of the days of the week in the Bengali Calendar are based on celestial objects, or নবগ্রহ nôbogroho.

  • Monday: সোমবার Shombar after সোম Shom (a Lunar deity)
  • Tuesday: মঙ্গলবার Monggolbar after মঙ্গল Monggol (planet Mars)
  • Wednesday: বুধবার Budhbar after বুধ Budh (planet Mercury)
  • Thursday: বৃহস্পতিবার Brihoshpotibar after বৃহস্পতি Brihoshpoti (planet Jupiter)
  • Friday: শুক্রবার Shukrobar after শুক্র Shukro (planet Venus)
  • Saturday: শনিবার Shonibar after শনি Shoni (planet Saturn)
  • Sunday: রবিবার Robibar after রবি Robi (a Solar deity)

In the Bengali calendar, the day begins and ends at sunrise , unlike in the Gregorian calendar, where the day starts at midnight.

Revised Bengali Calendar

The Bengali Calendar in Bangladesh (then East Pakistan) was modified by a committee headed by the celebrated scholar Dr. Muhammad Shahidullah under the auspices of the Bangla Academy of East Pakistan, now Bangladesh, on 17 February 1966.

The length of a year in the Bengali calendar, as in the Gregorian calendar, is counted as 365 days. However, the actual time taken by the earth in its revolution around the sun is 365 days 5 hours 48 minutes and 47 seconds. To make up this discrepancy, the Gregorian calendar adds an extra day, to make a leap year, to the month of February every fourth year (except in years divisible by 100 but not by 400). The Bengali calendar, which was based on astronomical calculations, did not make this extra leap year adjustment. Bengali months, too, were of different lengths. To counter this discrepancy, and to make the Bengali calendar more precise, the following recommendations of the Bangla Academy are followed:

  • The first five months of the year from Boishakh to Bhadro will consist of 31 days each.
  • The remaining seven months of the year from Ashshin to Choitro will consist of 30 days each.
  • In every leap year of the Gregorian calendar, an additional day will be added in the month of Falgun, which is just 14 days after 29th February. (Modified without material change).

The revised calendar was officially adopted in Bangladesh in 1987. However, it is not followed in the neighbouring state of West Bengal, India, where the traditional calendar continues to be followed due to the deep bond of Hindu culture with the Bengali calendar. Hindu religious festivals are celebrated based on a particular lunar day and Bengali calendar combination.

Revised and non-revised versions

The first of Boishakh, Pôhela Boishakh, is the Bengali New Year's Day. In West Bengal, it is celebrated on 14/15 April. However, since the calendar was revised in Bangladesh the new year now always falls on 14 April.

In West Bengal, India, the Bengalis follow a sidereal solar calendar unlike the tropical solar calendars, such as the revised Bengali and Gregorian Calendars. The mathematical difference between the sidereal and the tropical calendars accounts for the difference of starting the new year in Bangladesh and West Bengal, India. Because of this the length of the months are also not fixed in the Bengali sidereal calendar, but rather are based on the true movement of the sun.

Leap year

Although the sidereal solar calendar is followed in West Bengal, India, the number of days in the months are determined by the true motion of the Sun through the zodiac. In this calendar, seven is subtracted from the year, and the result is divided by 39. If after the division the remainder (= (year  - 7) / 39) is zero or is evenly divisible by 4, the year is then designated as a leap year and contains 366 days, with the last month, Choitro, taking 31 days. There are 10 leap years in every 39 years, although an extraordinary revision may be required over a long time.

According to the new calendar system in Bangladesh, Falgun (which begins mid-February) has 31 days every four years. To keep pace with the Gregorian calendar, the Bengali leap years are those whose corresponding Gregorian calendar year is counted as a leap year. For example, Falgun 1410 was considered a Bengali leap month, as it fell during the Gregorian leap month of February 2004.


The usage and popularity of the Bengali calendar in eastern South Asia is partly due to its adaptation to the unique seasonal patterns of the region. Eastern South Asia has a climate that is best divided into six seasons, including the monsoon or rainy season and the dry season in addition to spring, summer, fall, and winter.

In everyday use, the Bengali Calendar has been largely replaced by the Gregorian Calendar in Bengali-speaking regions, although it is still essential for marking holidays specific to Bengali culture (e.g. Pôhela Boishakh, Durga Puja, etc.), and for marking the seasons of the year. The Bengali calendar is recognized by the government of Bangladesh, whose offices date all their correspondence with the Bengali date as well as the Gregorian one. Almost every Bengali- and English-language newspaper in Bangladesh and West Bengal prints the day's date according to the Bengali Calendar alongside the corresponding date of the Gregorian Calendar. Many newspapers in Bangladesh also add a third date, following the Islamic Hijri Calendar. Thus, it is quite common in Bangladesh to find the date written three times (e.g. "25 Falgun 1412, 17 Muharram 1427, 27 February 2006") under the newspaper title.

Related calendars

The Bengali calendar is related to the Hindu solar calendar, which is itself based on the Surya Siddhanta. The Hindu solar calendar also starts in mid-April, and the first day of the calendar is celebrated as the traditional New Year in Assam, Kerala, Manipur, Nepal, Orissa, Punjab, Tamil Nadu, and Tripura in addition to Bengal, Indian state of West Bengal and Bangladesh. Nepal, Thailand and Sri Lanka also celebrate new year around the same time (12-15 April). This is also known as Mesha Sankranti.


  1. ^ Majumdar, Ramesh C. (1943). The History of Bengal. Dacca. pp. 58-68. ISBN 81-7646-237-3.  
  2. ^ page-331 to page-333, The Argumentative Indian, Author: Amartya Sen, ISBN 0-141-01211-0
  3. ^ According to the unrevised calendar used in India

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