Here is a Bengali calendar showing some, mainly hindu religious, events following the Gupta press tradition. If you are on a Mac before Mountain Lion, you may need to install Bengali to see this correctly.

Bengali Calendar (বাংলা ক্যালেণ্ডার)

According to some traditions, on the bengali new year (1 vaizAkha; guptapress) of san 1409 that started on 15 April 2002 AD, Indian national 25 caitra 1924, assamese bhAskarAbda 1 vahAg 1409, faslI (this starts on bhAdra kRSNA pratipada) 18 cait 1409, saMvat 3 caitra su 2059 (caitrAdi, kArttikAdi would be 2058), heijri 1 safar 1423, and in Amli 1409 (this starts on bhAdra shuklA dvAdashI) magI 1364, tripurAbda 1412, caitanyAbda 516, kAmrUpiYa zrIzaGkabda 553, zrIbuddhAbda 2545, mahAvIra nirvANabda 2528, nimbArkAbda 5097, nAnakAbda 533, we were in the 5104^th year of the current kaliyuga, which is only a small part of the current caturyuga (43,20,000 years: the traditional Indian counting system groups in successive hundreds after the first thousands), and were in the 1,97,29,49,075th year of the current svetavarAhakalpa (lasting 4,32,00,00,000 years). Alternatively, from the traditional sUryyasiddhAnta beginning of counting on a spring equinox on saturday, 7,14,40,41,60,541 days had passed before this year started. Also, 1,50,122 days had passed since another starting point (gauD.IYa dinavRnda; ayanAMza 22.32.41.40; vIjAMza 1.42.3.36).

Be that as it may, the common Bengali calendar era, usually called san (সন) or baGgAbda (বঙ্গাব্দ), effectively counts from 594 A.D., which would be about the time shashAGka (শশাঙ্ক) was ruling in Bengal; but that is, in all likelihood, coincidental: no known historical event of his reign falls on that date. It is possible that bhASkaravarmaNa (ভাস্করবর্মা) of prAgjyotiSapura (প্রাগ্জ্যোতিষপুর) ascended to the throne on that year and led to the bhAskarabda (ভাস্করাব্দ) still used in Assam; and this may have influenced the Bengali choice. However, it is usually considered to be an adaptation of the tArikh ilAhi (তারিখ ইলাহি) calendar introduced by akbar in 1584 A.D. (10/11 March of the 29th year of his reign is probably in 1585?: it is certainly 992 Anno Heijira): to arrive at the era he started his solar calendar such that in his year of ascension to the mughal throne (10th of Rabi 'ul Awal of 963 A.H., 1556 A.D., shaka 1479, vikrama samvat 1614) the san was the same as the heijira (and the lunar vaishAkha was essentially the same as the first month of the muslim new year, muharram). Though the tArikh ilAhi calendar—with the months Karwadin, Ardi, Vihisu, Khordad, Teer, Amardad, Shahriar, Aban, Azur, Dai, Baham and Iskander Miz, after (it looks like current Ordibehesht is split into two, and current Mihr is missing in the previous list: need to check) the Persian month names which currently are Farvardīn فروردین (‘guardian angel,’ related to Farevashi, guardians of humans), Ordībehesht اردیبهشت (‘ultimate rightness,’ related to Asha Vahishta, lord of fire and noontime heat), Khordåd خرداد (‘wholeness,’ related to Haurvatat, protector of waters), Tīr تیر (‘swift one,’ related to Tishtrya, lord of scribe), Mordad مرداد (‘immortality,’ related to Ameretat, supporter of plant life), Shahrīvar شهریور (‘desirable dominion,’ related to Khashtra Vairya, lord of sky, stone, metals, warriors, and protector of the weak), Mehr مهر (‘loyalty,’ related to Mithra, yazata of the covenant), Åbån آبان (‘waters,’ related to Apas, protector Eyzad of the waters), Åzar آذر (‘fire,’ related to Atar/Adur, yazata of fire), Dey دی (‘creator,’ related to dadar), Bahman بهمن (‘good purpose,’ related to Vohu Manah, protector of animals and cosmic order), and Esfand اسپند (‘holy devotion,’ related to Spenta Armaiti, protector of mother earth, guardian o herdsmen and farmers)—died out soon, the corresponding Bengali calendar (fasli) maintained the same era, though it was based on sUryya siddhAnta (as was the shaka calendar which formed the basis of it and the Indian National Calendar used today), and the number of days in the months vary from year to year as explained below. Obviously, being a solar calendar, it diverged from the hejira, a completely lunar calendar, by about 1 year every 33 years, so that in 1407 san, it was 1421 hijri.

Being a truly solar calendar, the number of days in a month is not fixed conventionally. The ecliptic (the apparent path of the sun, moon, and the planets in the sky: as their orbits are roughly coplanar, they describe a band across the sky) is divided into 27 nakSatras ((নক্ষত্র); each 13 degrees 20 minutes) and 12 rASis ((রাশি); each 30 degrees). The nakSatras—3 kRttikA (কৃত্তিকা), 4 rohiNI (রোহিণী) = brAhmI (ব্রাহ্মী), 5 mRgazIrA (মৃগশীরা) = AgrahAYaNI (অগ্রহায়ণী), 6 ArdrA (আর্দ্রা), 7 punarvasU (পুনর্বসূ) = yAmakau (যমকৌ), 8 puSYA (পুষ্যা) = sidhyA (সিধ্যা) = tiSyA (তিষ্যা), 9 AshleSA (আশ্লেষা), 10 maghA (মঘা), 11 pUrva phalgunI (পূর্বফাল্গুনী), 12 uttara phalgunI (উত্তরফাল্গুনী), 13 hasta (হস্তা), 14 citrA (চিত্রা), 15 svAtI (স্বাতী), 16 vishAkha (বিশাখা) = rAdhA (রাধা), 17 anurAdhA (অনুরাধা), 18 jyeSTha (জ্যেষ্ঠা), 19 mUla (মূলা), 20 pUrvASADh.A (পূর্বাষাঢ়া), 21 uttarASADh.A (উত্তরাষাঢ়া), 22 shravaNa (শ্রবণা), 23 shraviSThA (শ্রবিষ্ঠা) = dhaniSThA (ধনিষ্ঠা), 24 shatabhishak (শতভিষক্‌), 25 pUrva bhadrapada (পূর্বভদ্রপদ) = pUrva proSThapAda (পূর্বপ্রোষ্ঠপদ), 26 uttara bhadrapada (উত্তরভদ্রপদ) = uttara proSThapAda (উত্তরপ্রোষ্ঠপদ), 27 revatI (রেবতী), 1 ashvinI (অশ্বিনী), 2 bharaNI (ভরণী)—are named after a prominent star cluster within it (sometimes, a twenty-eighth nakSatra, abhijit (অভিজিত্‍), is named just before shravaNa), and the rASis—0 meSa (মেষ) = Aries, 1 vRSava (বৃষভ) = Taurus, 2 mithuna (মিথুন) = Gemini, 3 karkaTa (কর্কট) = Cancer, 4 siMha (সিংহ) = Leo, 5 kanyA (কন্যা) = Virgo, 6 tulA (তুলা) = Libra, 7 vRshcika (বৃষ্চিক) = Scorpio, 8 dhanuH (ধনুঃ) = Sagittarius, 9 makara (মকর) = Capricorn, 10 kumbha (কুম্ভ) = Aquarius, 11 mIna (মীন) = Pisces—after a prominent constellation. The beginning and end of a month is decided by the apparent position of the sun within this zodiac (each month lasting 30 degrees), or rather by using formulae for calculating the same. The major beginning of this system of calculation in India, probably of sumerian origin, goes back to the fifth century sUryya siddhAnta (সূর্য্যসিদ্ধান্ত), corrected in bengal by raghunandana's (রঘুনন্দন) aSTaviMshatitattva (অষ্টবিংশতিতত্ব) and by rAghavAnanda cakravartti's (রাঘবানন্দ চক্রবর্ত্তী) siddhAnta rahasya (সিদ্ধান্তরহস্য) and dinacandrikA (দিনচন্দ্রিকা) dating to 1591 and 1599 AD respectively. Today this has drifted from the true positions by some five or six hours on average, and this sometimes interacts with intercalary months in the religious calendar leading to the same festival being celebrated a month apart. Fortunately, everyone agrees as to the date in the non-religious one up to variation of one in the date, and the traditional formula—used by the gupta press panjika (গুপ্তপ্রেস পঞ্জিকা)—is in far more common use than the more accurate one—used by the vishuddha siddhAnta paJjikA (বিশুদ্ধসিদ্ধান্ত পঞ্জিকা) promulgated in 1890 AD—that follows the dRk siddhAnta (দৃক্‌‌সিদ্ধান্ত): so named because of the guiding principle that calculational rules must be modified to match observations. It is perhaps unfortunate that the official government attitude (as demonstrated in announcing dates for the religious festivals, for example: the bengali dates are actually rarely used in official documents) has followed this popular usage, whereas two of the major newspapers and an associated publishing house has moved over to the more accurate system.

This system (i.e. a siderial year, currently consisting of 365.256363004 mean solar days on January 1.5, 2000) keeps the seasons in synchronization with the months (which defines the tropical year consisting of about 365.242189669781 − 6.161870 × 10⁻⁶ T − 6.44 × 10⁻¹⁰ T² days, where T is in centuries of 365.25 ephemeris day Julian years from January 1.5, 2000, which a different source gives as 365.242190402 mean solar days on the same date; and forming the basis of the Gregorian calendar), except for a small detail: the axis of rotation of the earth precesses by about 1 nakSatra every 960 years (or roughly by one month every two millenia). Incidentally, other possible choices of the year which take into account the nutation of the axis (that does not affect the mean length of the year: the axial tilt moves between 21.5° and 24.5° in a 41000 year cycle), precession of the orbit (that defines a different, ‘anomalistic’ year: The 26000 year axial precession leads to the slightly faster 21000 year relative precession of the axis and the orbit), the change of the eccentricity of the orbit (between 0.005 and 0.058 in various cycles: 413000 year, 136000 year, and 95000 year periods), and the orbital inclination (This has a 70000–100000 year period) have no effect on the seasons. In the different Indian traditions, attempt has been made to start the year (and the counting of the nakSatras) near one of the equinoxes—this lead to the ‘first’ nakSatra marking the vernal equinox shifting back from mRgashIra to rohiNI to kRttika, and ultimately to the current usual counting starting with ashvinI (and, correspondingly as explained below, the current hindu calendar starts in caitra). (Actually, as explained later, a solar month is named after the amAnta lunar month which begins in it, which, in turn is named after the naKsatra which coincides with the full moon in it, and so the nakSatra that ‘marks’ the vernal equinox is after it by upto about 15°.)

As the apparent speed of the sun varies during the year (currently faster during the current winter in the northern hemisphere), and also slightly from year to year, the number of days in a month varies between 29 and 32 days. Usually now, the northern hemisphere winter months are 30 days and the summer months are 31 days each.

To summarize, as described in the table below, the months of the year (vaishAkha, jyaiSTha, ASADh.a, shrAvaNa, bhAdra, Ashvina, kArttika, agrahAYaNa, pauSa, mAgha, phAlguna, caitra) (বৈশাখ, জ্যৈষ্ঠ, আষাঢ়, শ্রাবণ, ভাদ্র, আশ্বিন, কার্ত্তিক, অগ্রহায়ণ, পৌষ, মাঘ, ফাল্গুন, চৈত্র) are unequal in length and are named after twelve of the naKSatras, the months were originally named by a neighbouring nakSatra when the moon was full (the first listed naKSatra, kRttikA, corresponds to the seventh month because sun and moon are on opposite sides during the full moon). vaishAkha starts on that day (always counted sunrise to sunrise) on whose sunset the apparent sun's longitude is first past 23 degrees and 15 minutes (thus entering meSa); its being the first month of the year might have been the original shaka calendar tradition or influenced by the tArikh ilAhi, and reinforced by the tradition of siddhArtha gautama buddha having been born on the full moon of lunar vaishAkha (which will be in the solar jaiSTha); the month is also related to his attaining enlightenment and death, as also to the birth of mahavIra jaina. The months are always a whole number of days, but they vary from year to year in length. Similarly, their correspondence with the Gregorian calendar also varies from year to year; though the overall drift is small (about 1 day every 71 years) because it is the difference between sidereal and tropical year, which is very small. Over the years, the difference, however, does build up; and the correspondence between the months and seasons has to be reworked. Thus, the six seasons—Hot grISma (গ্রীষ্ম), Rainy varSA (বর্ষা), Ripening sharat (শরত্‍), Frosty hemanta (হেমন্ত), Frozen shIta (শীত), and Brilliant vasanta (বসন্ত)—are associated with pairs of months, but whether the sequence starts in vaishAkha (more common in bengal today) or jyaiSTha varies according to tradition. Note that bengal is actually in the tropical monsoon region, and the names of the cold months are merely etymological—most people will think of and translate shIta as cold rather than frozen!

As an example, currently (i.e. when the page was first written in Feb 2000), the Bengali year is 1406. The number of days in each month, and when they started (relative to the Gregorian calendar) are stated below for this year and two years preceding (others have been added since this was written). The difference between the two prevalent calculational systems explained above this year is that according to vishuddha siddhAnta, Ashvina and mAgha each have 30 days each, so the dates in kArttika, agrahAYaNa, pauSa and mAgha are shifted by one day each. Remember though that the day starts at sunrise: so 1 AM on 15 Apr 1999 is still 1 AM 30 caitra 1405 according to Bengali counting. However, 6 AM on 15 Apr 1999, the new year has already started.

For keeping time within the day, the use of the common system (with the clock counting in hours from the usual conventional midnight or midday) is the one in common use; in the traditional system, sunrise to sunrise divided into 60 ghaTis (1 ghaTi = 1 daNDa = 60 pala = 3600 vipala = 216000 anupala), or the same approximately 24 hours being divided into 8 yAmas=praharas of 3 hours each and 30 muhUrtas of 48 minutes each. The definitions of the smaller units, 1 muhUrta/kSaNa = 2 nAD.ika = 30 kalA, 1 kalA = 30 kASThA, 1 kASThA = 15 nimeSa, have been considerably variable (kalA instead of 1/60 of a muhUrta, has also been 1/360th of a muhUrta, 10/201 of a muhUrta or 1/903 of 24hours; kASThA has sometimes been 1/12, 1/15 or 1/124 of a kalA instead; kalA has also been called laghu, nAD.ikA has been 1/6 or 1/7 a prahara; vikalA has been 1/60 of a kala or a daNDa; some of this is due to astronomy confounding units of angle and time; in addition one has 1 vinAD.I = 1/60 nAD.I or nAD.ikA = 6 prANa, thus fifteen prANa or breaths correspond to a minute, which matches the usual adult respiratory rates or 12–20) over time and find mention in some common phrases and religious ceremony. Similarly, the subannual divisions, as well as the time units larger than a year (yUga, kalpa and manvAntara, and the pitR, deva and brAhma years) are quite irrelevant here.

The current calendar also uses the seven day week standard all over the world. The origins of these goes back to the ancient Egyptians, who ordered the five visible planets along with the sun and the moon into the ‘Chaldean order’: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon in increasing order of their apparent speed or ‘skittishness’ (see here for a nice animation of the ‘Dance of the planets’), which was probably considered as the decreasing order of their steady influence. In the duodecimal system in use then, the daytime and the nighttime were each divided into a dozen periods (this ultimately gave us the 24 hours in a day), each presided in sequence by one of these ‘planets’. The first period of light on each successive day was, thus, presided over by the cycle of planets: Saturn, Sun, Moon, Mars, Mercury, Jupiter, and Venus; and this is the order used for the names of the days of the week. Except, of course, the names for the weekdays, called vAra (বার, from the root vR, to choose, meaning the chosen day), used are Bengali with Sanskrit etymologies: shani (শনি, probably ultimately from the root sham, to work or fatigue, whence to be calm; this probably refers to the slow movement), ravi (রবি, said to be from ru, to roar, but probably connected with a lost rash, to weave, because of the common metaphor of a woven rope for rays), soma (সোম, from the root su, to press, it originally meant juice; but the milky drop of the common libation became a popular metaphor for the moon), maGgala (মঙ্গল, from a root maGg to move, it may have originally meant fast mover, but the attested meaning is blessed), budha (বুধ, from a root for perception, meaning awaking), bRhaspati (বৃহস্পতি, from the roots bRh to speak, whence prayer and pat, to master; meaning lord of prayers), and shukra (শুক্র, from root shuc, to shine, meaning shining). The week, however, conventionally starts with Sunday rather than Saturday as listed here.

For religious purposes, a luni-solar calendar is also used (and this is the so-called Hindu Calendar whose vikrama/mAlava/kRta sam.vatsara era starts in 58 B.C., not clear why. It may conceivably be related to Azes I.), which usually starts with the new moon of caitra (and hence called caitrAdi; some jains follow a kArttikadi vikrama samvat in adition to the kArttikAdi vIraa nirvANa samvat starting with the traditional date of the death of mahAvIra jaina on kArttika amAvaSyA of 528 BC). In this calendar, months are synodic, i.e. determined by the phases of the moon–actually, by the angular distance between the sun and the moon as seen from the earth. In this luni-solar calendar the start and end of the lunar days, or tithi (তিথি), are defined by requiring that the distance between the sun and the moon change by 12 degrees; so their actual length is between 20 and 27 hours. The tithis in a given month are named from shuklA (শুক্লা) (meaning bright) 1 through shuklA 15 and then kRSNA (কৃষ্ণা) (meaning dark) 1 through kRSNA 15. The 14 days of each half, or paKSa (পক্ষ) (literally flank), other than the new moon, amAvasyA (অমাবস্যা) (dwelling together) that ends the kRSNa paKSa or full moon, or pUrNimA (পূর্ণিমা) (fullness), that ends the shukla paKSa are usually referred to by the bengalee versions of the Sanskrit feminine ordinals: pratipada (প্রতিপদ) (this word is an exception and does not mean first; in saMskRta it meant beginning or entrance), dvitIYA (দ্বিতীয়া), tritIYA (তৃতীয়া), caturthI (চতুর্থী), paJcamI (পঞ্চমী), SaSThI (ষষ্ঠী), saptamI (সপ্তমী), aSTamI (অষ্টমী), navamI (নবমী), dashamI (দশমী), ekAdasI (একাদশী), dvAdasI (দ্বাদশী), traYodasI (ত্রয়োদশী), and caturddasI (চতুর্দ্দশী). When solar days are named by a tithi, it refers to the tithi at sun rise.

There are two system of counting the months, the purNimAnta (পূর্ণিমান্ত) system that ends with the full moon, is popular in Bengal. In normal cases, the month is named by the solar month starting around (previous new moon to next new moon) the pUrNimA at which it ends. If no solar month starts in this period, then that entire period including this full moon, i.e., starting after the previous new moon and until the next new moon, is deleted from counting, and considered intercalary, mala (মল মাস) or ‘dirty’, month. The next month effectively becomes twice as long, with its middle portion (after the first new moon to the next new moon) distinguished with a adhika (অধিক) or ‘extra’, prefixed to it, To clarify, the normal months can have nija (নিজ) or ‘own’ prefixed to them. This is a normal occurence every couple of years, but occasionally the opposite happens: two solar months start in the same period. In this case, the new moon to new moon period surrounding the next month are called kSaYa (ক্ষয়) or ‘decayed’ month, and the name of the missing (the one starting later) month is suffixed (before full moon) or prefixed (after the full moon) to the names of the appropriate months. Of course, it is completely possible that one can have an intercalary immediately followed by a decayed month (or the opposite), but the situation occurs extremely rarely. When a rule calls for a particular day (phase of the moon) of the month, the nija version of the month is chosen if possible. Overlapping months created by kSaYa are chosen as a last resort, one chooses an adhika over it if possible.

The other system notes that if the start of a month is delayed till the new moon, the intercalary and decayed month names simplify enormously. It started around the 1^st century BC. In this system, the kRSNa pakSa is named in the previous month. So, now the month ends with the new moon, and it is called amAnta (অমান্ত). The adhika mAsa in this system, then completely precedes the nija mAsa, and the kSaYa mAsa overlaps completely the previous month only.

The years are arranged in a 60 year cycle with the names 1 prabhava, 2 vibhava, 3 shukla, 4 pramoda, 5 prajApati, 6 AMgirasa, 7 shrImukha, 8 bhAva, 9 yuvan, 10 dhAtR, 11 Ishvara, 12 bahudhAnya, 13 pramAthin, 14 vikrama, 15 vRSa, 16 citrabhAnu, 17 svabhAnu, 18 tAraNa, 19 pArthiva, 20 vyaya, 21 sarvajit, 22 sarvadhArin, 23 virodhin, 24 vikRta, 25 khara, 26 nandana, 27 vijaYa, 28 jaYa, 29 manmatha, 30 durmukha, 31 hemalambin, 32 vilambin, 33 vikArin, 34 shArvari, 35 plava, 36 shubhakRt, 37 shobhana, 38 krodhin, 39 vishvAvasu, 40 parAbhava, 41 plavaMga, 42 kIlaka, 43 saumya, 44 sAdhAraNa, 45 virodhikRt, 46 paritApin, 37 pramAdin, 48 Ananda, 49 rAkSasa, 50 anala, 51 piMgala, 52 kAlayukti, 53 siddhArthin, 54 raudra, 55 durmati, 56 dundubhi, 57 rudhirodgArin, 58 raktAkSa, 59 krodhana, 60 kSaYa.

Religious ceremonies also take into account the nAkSatra (নাক্ষত্র) month (siderial lunar month determined by position of the moon in the zodiac).

Note that the Bengali calendar is different from the Indian national calendar (established on Mar 22, 1957) which uses the same names for the months, and which is the official calendar all over India, including Bengal. That calendar always has 31 days in the months of vaisAkha through bhAdra, 30 days in Ashvina through phAlguna and 30/31 days in caitra depending on whether it is a leap year. The leap years of this calendar are synchronized with the leap years of the Gregorian calendar. It starts on the first of caitra which is March 22 of the Gregorian calendar (Mar 21st in a leap year), and uses the shaka/shAlivAhana varSa (শক/শালিবাহন বর্ষ) era starting in 78 A.D (may be related to kaniSka's accession to throne).

In addition, there are completely lunar calendars used by the muslims (the heijira calendar with the months muharram (محرم, মহরম, meaning forbidden), safar (صفر, শফর, meaning related to empty), rab'i al-awwal (ربيع الأول, রবি উল আউল, meaning beginning of the quarter/spring), rab'i al-thani/akhira (ربيع الثاني, রবি অল সানি, meaning repeat/second or end of the quarter/spring), jumada al-oula (جمادى الأولى, জমাদা অল আউল, meaning beginning of the freeze), jumada al-akhira/thani (جمادى الآخرة, জমাদা অল সানি, meaning end of the freeze), rajab (رجب, রজব, meaning feared/revered), sha'ban (شعبان, শাবান, meaning related to disperse), ramadan (رمضان, রমজান, meaning scorched), shawwal (شوال, শওয়াল, meaning related to rise), dhu al-q'adah (ذو القعدة, জেল্কদ, meaning the one of sitting), and dhu al-hijjah (ذو الحجة, জেলহজ্জ, meaning the one of pilgrimage)) and the vaiSNavas (followers of Shri Chaitanya) in bengal, the amAnta months in the latter—viSNu, madhusUdana, trivikrama, vAmaNa, shrIdhara, hRSikesha, padmanAbha, dAmodara, keshava, nAraYaNa, mAdhava, govinda (worker বিষ্ণু, killing demon of honey/mead মধুসূদন, three steps ত্রিবিক্রম, dwarf বামণ, holding flame=fortune শ্রীধর, master of senses—perhaps originally thrilled=bristled hair—হৃষীকেশ, lotus at point of bursting=navel পদ্মনাভ, subduer=rope at belly দামোদর, with hair কেশব, son of man নারায়ণ, related to honey/mead=spring or descendant of madhu=honey/mead মাধব, cow finder গোবিন্দ)—are named after the many names of viSNu. But even when they use the same names for the months, the calendars used in India differ due to the use of solar versus lunisolar, the different corrections put into the formulae which determines the asronomical events defining the months, the year beginning on different months, and their eras (i.e. the year 1) being different. However, the tradition of luni-solar calendars is very old: indications dating back to the Vedic period can be found, though details are available only from a few centuries B.C. A related tradition gave the parsees in India their version of the luni-solar calendar, which, however, is drifting fast because the tradition of leap years was stopped a long time back. The solar calendars, as mentioned above. are of later origin.