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The Bengali calendar (Bengali বঙ্গাব্দ Bônggabdo or বাংলা সন Bangla Shôn, Assamese: Vaskar), is the traditional calendar used in Bangladesh and eastern regions of India in the state of West Bengal,  and Tripura. The calendar is based on the solar year. The year begins on Pôhela Boishakh, which falls between April 13 and April 15.


The new Fôsholi Shôn was introduced on March 10 / March 11, 1584, Before the introduction of the Bengali Calendar, 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, the Mughal Emperor Akbar, who ruled from 1556 AD until 1605 AD, 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.

The new Fôsholi Shôn was introduced on March 10 / March 11, 1584, but was dated from Akbar's accession to the throne in 1556. The new year subsequently became known as বঙ্গাব্দ Bônggabdo or বাংলা সন Bangla Shôn ("Bengali year").

During the reign of the Mughals, the Bengali Calendar was officially implemented throughout the empire. Apart from Bengal, however, the calendar was abandoned with the end of Mughal rule.

That is just a myth among the Muslims of Bangladesh that Akbar implemented the calendar. During the Islamization process of Bangladesh after 1947, Bengali intellectuals from Bangladesh propagated this myth. Also it should be noted that New year day is celebrated between April 13th-15th in Bengal, Assam, Nepal, Sri Lanka and Thailand. Obviously Akbar did not start calendar in countries like Sri Lanka, Nepal and Thailand. It can be noted that Hindus in Bengal are thoroughly linked with the Bengali calendar in terms of their festivals unlike their Muslim counterpart. Also, the names of the Bengali months are same as in the Indian calendar. There is no authenticity of Akbar's involvement with Bengal during his rule. Bengal was mostly ruled by local kings during Akbar's time.

In a different interpretation, King Shashanka of Ancient Bengal, who ruled approximately between 600 AD and 625 AD, was credited with starting the Bengali era. Shashankya 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 prevailing reason is that an era can’t start as 963 B.S. (Bangla Shôn) in synchrony with 963 Hijra. The Bengali Era must have prevailed before that and Akbar took over form this point on. According to this the starting point of Bengali Era was AD 593/594. By the time of reign of Akbar in AD 1556 the Bengali Era 963 B.S. had been in synchrony with then used 963 Hijra era. Because of the practical advantages of using solar year, Akbar started using the Bengali era as the official calendar for collecting taxes. Extrapolating further back to the starting point of Bengali era it could be stated that it started on Monday, April 12, 594 in the Julian Calendar and Monday, April 14, 594 in the proleptic Gregorian calendar.

One important point is also claims consideration. King Akbar started counting Bangla Shon from 963 Hijri. As discussed above for backward synchronizatio, it's starting point calculated as 594AD. It's a historical truth that Hijrah started from 623/624AD with the Month of Muharram as starting point, it was middle of the year 623/624 in Gregorian calender. We find difference in between 594 & 623/624 is 29/30 years plus/minus six months. Bangla (Solar) year counts of 365 days and Hijri (Lunar) is 354 days, so the difference comes 11 days per year. Hence 963 years in backward calculation takes/gains approx 963x11=10593days which is equal to [10593/354=29.92..=] 30 Hijri(Lunar) years, exactly corresponds to the Year of Hijri starting point.

So it can be concluded that Bangla Year is based on Hijri [The historical HIJRAH FROM MAKKAH TO MADINA]. This also supports the opinion "Shashankya was the Introducer of Bangla Calendar",

If it is taken 593/594AD as starting point, "Shashankya as the Introducer of Bangla Calendar" is simply thrown out.

Months and Seasons[]

Organization of months[]

The Bengali calendar consists of 12 months and 6 seasons. Two months are paired together for each season and are organized as follows:

বঙ্গাব্দ Bônggabdo
Bengali Calendar

মাস Māsh
কাল/ঋতু Kāl/Ritu
বৈশাখ Boishakh
গ্রীষ্ম Grishsho
জৈষ্ঠ্য Joishţho
আষাঢ় Ashaŗh
বর্ষা Bôrsha
Rainy (Monsoon)
শ্রাবণ Srabon
ভাদ্র Bhadro
শরৎ Shôrot
আশ্বিন Ashshin
কার্তিক Kartik
হেমন্ত Hemonto
অগ্রহায়ন Ôgrohaeon
পৌষ Poush
শীত Šit
মাঘ Magh
ফাল্গুন Falgun
বসন্ত Bôshonto
চৈত্র Choitro#March-April

Naming of the months[]

The name of the months of Bengali calendar is based on the names of the নক্ষত্র nokkhotro (lunar mansions) - locations of the moon with respect to particular stars during the lunar cycle. It is presumed that these names were derived from the Shakabda, another calendar of this region which was introduced in the Shaka Dynasty. The naming of the months is as follows:

  1. বৈশাখ Boishakh after the star, বিশাখা Bishakha (Librae)
  2. জ্যৈষ্ঠ Joishţho after the star, জ্যেষ্ঠ Jeshţho (Scorpionis)
  3. আষাঢ় Ashaŗh after the star, অষাঢ়া Ôshaŗha (Sagittarii)
  4. শ্রাবণ Srabon after the star, শ্রাবণ Srabon (Aquilae)
  5. ভাদ্র Bhadro after the star, ভাদ্রপদা Bhadropôda (Pegasi and Andromedae)
  6. আশ্বিন Ashshin after the star, অশ্বিনী Ôshshini (Arietis)
  7. কার্তিক Kartik after the star, কৃত্তিকা Krittika (Pleiades)
  8. অগ্রহায়ন Ôgrohaeon after the star, অগ্রাইহন Agraihon
  9. পৌষ Poush after the star, পুশ্য Pushsho (Cancri)
  10. মাঘ Magh after the star মঘা Môgha (Regulus)
  11. ফাল্গুন Falgun after the star, ফাল্গুনী Falguni (Leonis and Denebola), and
  12. চৈত্র Choitro after the star, চিত্রা Chitra (Spica)

The month names in the initial Bengali calendar were different from those used in the modern version. Originally, the months were known as Karwadin, Ardi, Vihisu, Khordad, Teer, Amardad, Shahriar, Aban, Azur, Dai, Baham and Iskander Miz.

Days of the week[]

The Bengali Calendar incorporates the seven-day week as used in 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 (Mars)
  • Wednesday: বুধবার Budhbar after বুধ Budh (Mercury)
  • Thursday: বৃহস্পতিবার Brihoshpotibar after বৃহস্পতি Brihoshpoti (Jupiter)
  • Friday: শুক্রবার Shukrobar after শুক্র Shukro (Venus)
  • Saturday: শনিবার Shonibar after শনি Shoni (Saturn)
  • Sunday: রবিবার Robibar after রবি Robi (a Solar deity)

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

The Revised Bengali Calendar[]

The Bengali Calendar was modified by a committee headed by the celebrated scholar Dr. Muhammad Shahidullah under the auspices of the Bangla Academy on February 17, 1966. The Committee made some recommendations regarding the different problems facing rural Bengali cultural traditions due to changes of months and seasons.

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 century years and not divisible 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.
  • After each fourth year, an additional day will be added in the month of Falgun, as discussed below.

The revised calendar is officially adopted in Bangladesh. However, it is not followed in the neighbouring state of West Bengal, India, where the old calendar continues to be followed.

Leap year[]

According to the new calendar system, 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.

Revised and non-revised versions[]

The first of Boishakh, Pôhela Boishakh, is the Bengali New Year's Day. In Bangladesh, it is celebrated on April 14 every year according to the reformed calendar prepared by the Bangla Academy. However, since the people of the West Bengal follow the non-reformed calendar, which is not fixed with respect to the Western calendar, Indian Bengalis celebrate New Year's Day on April 15.

In West Bengal, India the Bengalis follow a sidereal solar calendar unlike the tropical solar calendars, such as the reformed Bengali and Gregorian Calendars. The mathematical difference between the Sidereal and the Tropical calendar amounts to 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 Bengali Sidereal calendar, but rather based on the true movement of the sun.


The usage and popularity of the Bengali calendar in eastern South Asia are partly due to its adaptation to reflect 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 with 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, and is thus recognized by the Bangladeshi government for the observation of public holidays. Almost every Bangla and English-language newspaper in Bangladesh and West Bengal prints the day's date according to the Bangla Calendar alongside the corresponding date in the Gregorian Calendar. Many newspapers in Bangladesh also add a third date, following the Islamic Hijri Calendar. In Bangladesh, it is quite common to find the date written three times (e.g. "25 Falgun 1412, 17 Muharram 1427, 27 February 2006") under the newspaper title.