>> From uia.ac.be!donche2 Thu Mar 3 02:11:16 1994 >> From: "PieterAV.Donche" >> Subject: Re: Julian vs. Gregorian Calendar > Could this text be included in the ROOTS-L archive for other > ROOTS-L/soc.gen*s users? ---------------------------------------------------------------- ____ Pieter Donche E-mail: donche@uia.ac.be // /// \ Univ. Inst. Antwerpen /\ _/~ Rekencentrum A2.23 Voice: +32 (0)3.820.22.02 ~~/` EU Universiteitsplein 1, Fax : +32 (0)3.820.22.44 __\_ _ B 2610 Wilrijk /_/ \\\_/ Belgium (`) EUROPE =~ = This text is a copy from what can be found in the Encyclopedia Britannica about European and Middle-East calendars. A few ** NOTES have been added and a minor error corrected. ENCYCLOPAEDIA BRITANNICA: Early Calendar systems; Jewish and Muslim calendar -------------------------------------------------------------------------------- I. Early calendar systems Standard units and cycles Time determination by stars, sun, and moon Complex cycles The early Roman calendar The Jewish calendar The Muslim calendar II. The western calendar The Julian calendar The Gregorian calendar I. EARLY CALENDAR SYSTEMS ========================= STANDARD UNITS AND CYCLES ------------------------- The basic unit of computation in a calendar is the day, and although days are now measured from midnight to midnight, this has not always been so. Astronomers, for instance, from about the 2nd century AD until 1925 counted days from noon to noon. In earlier civilizations and among primitive peoples, where there was less communication between different settlements or groups, different methods of reckoning the day presented no difficulties. Most primitive tribes used a dawn-to-dawn reckoning, calling a succession of days so many dawns, or suns; and this system was continued by the Babylonians and Greeks, who counted a day from sunrise to sunrise. In Egypt, a midnight-to-midnight reckoning was adopted; the Jews and, later, the Italians counted from sunset to sunset. The Teutons counted nights, and from them the grouping of 14 days called a fortnight is derived. There was also great variety in the ways in which the day was subdivided. The Sumerians, for example, divided it into six watches, three during daylight and three during the night; the Jews adopted a similar method. The length of the watches was not constant but varied with the season, the day watches being the longer in summer and the night watches in the winter. Such seasonal variations in divisions of the day became customary in antiquity since they correspond to the length of the Sun's time above the horizon, at maximum in summer and minimum in winter. Only with the advent of mechanical clocks in western Europe at the end of the 13th century did seasonal (unequal) hours become inconvenient. Most early Western civilizations used 24 seasonal hours in the day - 12 hours of daylight and 12 of darkness. This was the practice of the Greeks, the Egyptians, and the Romans, and of Western Christendom so far as civil reckoning was concerned. The church adopted its own canonical hours for reckoning daily workshop: there were seven of these - matins, prime, terce, sext, none, vespers, and compline - but in secular affairs the system of 24 hours held sway. This number, 2 x 12, or 24, was derived from the Sumerian sexagesimal method of reckoning, based on gradations of 60 (5 x 12 = 60) rather than on multiples of 10, even though the 24-hour division of the day, and their hours were double hours, with only 12 to cover both day and night. They were among the few to have hours of the same length throughout the year because the Babylonians believed the Sun and Moon to travel through the same number of divisions in the sky during each day and night period. Once the day is divided into parts, the next task is to gather numbers of days into groups. Among primitive peoples, it was common to count moons (months) rather than days, but later a shorter period than the month was thought more convenient, and an interval between market days was adopted. It varied widely. In West Africa some tribes used a four-day interval; in central Asia five days was customary; the Assyrians adopted six days and the Egyptians, ten days, whereas the Babylonians attached particular significance to the days of the lunation that were multiples of seven. In ancient Rome there was a nundinae, or nine-day, period between weekly markets, although because of the Roman method of inclusive numeration a nundinae contained what would now be called eight days. The seven-day week may owe its origin partly to the four (approximately) seven-day phases of the Moon and partly to the Babylonian belief in hebdomadism - the sacredness of the number seven - which itself was probably related to the seven planets. Moreover, by the 1st century BC the Jewish seven-day week seems to have become adopted throughout the Roman world, and its exerted its due influence on Christendom. The origin of the names of the days of the week appears to be astrological and to have been derived from the Latin or Scandinavian god whose hour stated the day. The moon is based on the lunation, that period in which the Moon completes a cycle of its phases. Lasting approximately 29 1/2 days, it is easy to recognize and short enough for the days to be counted without using large numbers. In addition, it is very close to the menstrual period of women and also to the duration of cyclic behaviour in some marine creatures. Thus, the month possessed great significance and was often the governing period for religious observances, of which the dating of Easter is a notable example. All early calendars were, essentially, collections of months, the Babylonians using 29- and 30-day periods alternately, the Egyptians fixing the duration of all months at 30 days, with the Greeks copying them, and the Romans in the Julian calendar having a rather more complex system using one 28-day period with the others of either 30 or 31 days. The month is not suitable for determining the seasons, for these are a solar, not a lunar, phenomenon. Seasons vary in different parts or the world - in tropical countries there are just the rainy and dry periods, but elsewhere there are successions of wider changes. In Egypt, the annnual flooding of the Nile was followed by seeding and then harvest, and three seasons were recognized; but in Greece and other more northern countries there was a succession of four seasons of slightly different lengths. However many there seemed to be, it was everywhere recognized that seasons were related to the Sun and that they could be determined from solar observations. These might consist of noting the varying length of the midday shadow cast by a stick thrust vertically into the ground or follow the far more sophisticated procedure of deducing the Sun's position against the background of the stars. In either case the result was a year of 365 days, a period incompatible with the 29 1/2-day lunation. To find some simple relationship between the two was the problem that faced all calendar makers fron Babylonian times onward. TIME DETERMINATION BY STARS, SUN, AND MOON ------------------------------------------ Celestial bodies provide the basic standards for determining the periods of a calendar. Their movement as they rise and set is now known to be a reflection of the Earth's rotation, which although not precisely uniform, can conveniently be averaged out to provide a suitable calendar day. The day can be measured either by the stars of by the Sun. If the stars are used, then the interval is called the sidereal day and is defined by the period between two passages of a star (more precisely of the vernal equinox, a reference point on the celestial sphere) across the meridian: it is 23 hours, 56 minutes, 4.10 seconds of mean solar time (see below). The interval between two passages of the Sun across the meridian is a solar day. In practice, since the rate of the Sun's motion varies with the seasons, use is made of a fictitious Sun that always moves across the sky at an even rate. This period of constant length, far more convenient for civil purposes, is the mean solar day, which has a duration in sidereal time of 24 hours, 3 minutes, 56.55 seconds. It is longer than the sidereal day because the motion of the Earth in its orbit during the period between two transits of the Sun means that the Earth must complete more than a whole revolution to bring the Sun back to the meridian. The mean solar day is the period used in calendar computation. The month is determined by the Moon's passage around the Earth, and, as in the case of the day, there are several ways in which it can be defined. In essence, there are of two kinds: first, the period taken by the Moon to complete an orbit of the Earth, and, second, the time taken by the Moon to complete a cycle of phases. For astronomically primitive societies, orbital measures were too sophisticated, and the month was determined by noting the interval between the appearance of one thin crescent Moon and the next - in other words, from one new Moon to another. But however the phases are defined, the interval is now known to be 29.53059 days. Known as the synodic month, it is longer than the orbital month, just as the solar day is longer than the sidereal, and for a similar reason. It grew to be the basis of the calendar month. The year is the period taken by the Earth to complete an orbit around the Sun and, again, there are a number of ways in which this can be measured. But for calculating a calendar that is to remain in step with the seasons, it is most convenient to use the tropical year, since this refers directly to the Sun's apparent annual motion north and south; it is defined as the interval between successive passages of the Sun through the vernal equinox (i.e. when it crosses the celestial equator late in March) and amounts to 365.242199 mean solar days. The tropical year and the synodic month are incommensurable, 12 synodic months amounting to 354.36706 days, almost 11 days shorter than the tropical year. Moreover, neither is composed of a complete number of days, so that to compile any calendar that keeps in step with the Moon's phases or with the seasons it is necessary to insert days at appropriate intervals; such additions are known as intercalations. In primitive lunar calendars, intercalation was often achieved by taking alternately months of 29 and 30 days. When, in order to keep dates in step with the seasons, a solar calendar was adopted, some greater difference between the months and the Moon's phases was bound to occur. And the solar calendar presented an even more fundamental problem - that of finding the precise length of the tropical year. Observations of cyclic changes in plant or animal life were far too inaccurate, and astronomical observations became necessary. Since the stars are not visible when the Sun is in the sky, some indirect way had to be found to determine its precise location among them. In tropical and subtropical countries it was possible to use the method of heliacal risings. Here the first task was to determine the constellations around the whole sky through which the Sun appears to move in the course of a year. Then, by observing the stars rising in the east just after sunset it was possible to know which were precisely opposite in the sky, where the Sun lay at that time. Such heliacal risings could, therefore, be used to determine the seasons and the tropical year. In temperate countries, the angle at which stars rise up from the horizon is not steep enough for this method to be adopted, so that there wood or stone structures were built to mark out points along the horizon to allow analogous observations to be made. The most famous of these is Stonehenge in Wiltshire, England, where the original structure appears to have been built about 2000 BC and additions made at intervals several centuries later. It is composed of a series of holes, stones, and archways arranged mostly in circles, the outermost ring of holes having 56 marked positions, the inner ones 30 and 29, respectively. In addition, there is a large stone - the heel stone - set to the northeast, as well as some smaller stone markers. Observations were made by lining up holes or stones with the heel stone or one of the other markers and watching for the appearance of the Sun or Moon against that point on the horizon that lay in the same straight line. The extreme north and south positions on the horizon of the Sun - the summer and winter solstices - were particularly noted, while the innner circles, with their 29 and 30 marked positions, allowed "hollow" and "full" (29- of 30-day) lunar months to be counted off. To obtain other astronomical information, such as the advent of eclipses, observations were made from various different positions, especially those on the outer circle of stones. More than 600 contemporaneous structures of an analogous but simpler kind have been discovered in Britain and Britany, It appears, then, that astronomical observation for calendrical purposes was a widespread practice in some temperate countries three to four millennia ago. Today a solar calendar is kept in step with the seasons by a fixed rule of intercalation. But although the Egyptians, who used the heliacal rising of Sirius to determine the annual innundation ot the Nile, knew that the tropical year was about 365.25 days in length, they still used a 365-day without intercalation. This meant that the calendar date of Sirius' rising became increasingly out of step with the original dates as the years progressed. In consequence, while the agricultural seasons were regulated by the heliacal rising of Sirius, the civil calendar ran its own separate course. It was not until well into Roman times that an intercalary day once every four years was instituted to retain coincidence. Without such a rule, the agricultural calendar had to be determined solely by astronomical observation. COMPLEX CYCLES -------------- Although the incommensurability of months and years and the fact that neither occupied a whole number of days was recognized quite early in all the great civilizations, it was also appreciated that the difference between calendar dates and the celestial phenomena due to occur on them would first grow and then were once more in coincidence. The succession of difference and coincidences would be cyclic, recurring time and again as the years passed. An early recognition of this was the Egyptian Sothic cycle. The 365-day year used in the Egyptian calendar was in error with respect to the heliacal risings of the star Sirius (Sothis) by one quarter of a day per tropical year. This amounted to one day every four tropical years, or one whole Egyptian calendar year every 1,460 tropical years (4x365), which was equivalent to 1,461 Egyptian calendar years. After this period the heliacal rising and setting of Sothis would again coincide with the calendar dates (see below, the Egyptian calendar). The main use of cycles was to try to find some commensurable basis for lunar and solar calendars, and the most famous of all the early attempts was that usually attributed to Cleostratus of Tenedos (c. 500 BC) and Eudoxus of Cnidus (390-c.340 BC), often known as the octaeteris. Modern scolarship shows Cleostratus to be a somewhat shadowly figure, and it has also become clear that a cycle of this kind was adopted in Babylon between 529 and 504 BC. Whatever its exact origins, the cycle coverd eight years, as its name implies; and since in the 6th century BC the year was accepted to be 365 days in length, the octaeteris amounted to 8 x 365, or 2,920 days. This was very close to the total of 99 lunations (99x29,5 = 2,920.5 days), so this cycle gave a worthwhile link between lunar and scolar calendars. When, in the 4th century BC, the accepted length of the year became 365.25 days, the total number of solar calendar days involved became 2.922, and it was then realized that the octaeteris was not so satisfactory a cycle as supposed, since the 29.5-day lunation period was still used. Another early and important cycle was the saros, essentially an eclipse cycle. There has been some confusion over its precise nature because the name is derived from the Babylonian word shar of sharu, which could mean either "universe" or the number 3,600 (i.e. 60 x 60). In the latter sense it was used by Berosus (c. 290 BC) and a few later authors to refer to a period of 3,600 years. Its first astronomical use appears in an anonymous encyclopaedia called the Suda Lexicon (Suidas Lexicon), of about 1000 AD. There it was said to be a measure of 222 months used by the Chaldeans, and, although this cannot be quite correct, it is certainly clear that by the 4th century BC the Babylonians did know something of an 18-year or 216-month (18 x 22) cycle of eclipses. What is now known as the saros and appears as such in astronomical textbooks (still usually credited to the Babylonians) is a period of 18 years 11 1/3 days (or with one day more or less, depending on how many leap years are involved), after which a series of eclipses is repeated. In Central America an independent system of cycles was established. The most significant of all the early attempts to provide some commensurability between a religious lunar calendar and the tropical year was the Metonic cycle. This was first devised about 430 BC by the astronomer Meton of Athens. Meton worked with another Athenian astronomer, Euctemon, and made a series of observations of the solstices, when the Sun's noonday shadow cast by a vertical pilar, or gnomon, reaches its annual maximum or minimum, to determine the length for the tropical year. Taking a synodic month to be 29.5 days, they then computed the difference between 12 of these lunations and their tropical year. But months were measured in whole days, and Meton and Euctemon wanted a longterm rule that would be as accurate as they could make it, so they settled on a 19-year cycle. This cycle consisted of 12 years of 12 lunar months each and seven years each of 13 lunar months, a total of 235 lunar months. If this total of 235 lunations is taken to contain 110 hollow months of 29 days and 125 full months of 30 days, the total comes to (110 x 29) + (125 x 30), or 6,940 days. The difference between this lunar calendar and a solar calendar of 365 days amounted to only five days is 19 years and, in addition, gave an average length for the tropical year of 365.25 days, a much-improved value that was, however, allowed to make no difference to daily reckoning in the civil calendar. But the greatest advantage of this cycle was that it laid down a lunar calendar that possessed a definite rule for inserting intercalary months and kept in step with a cycle of the tropical years. It also gave a more accurate average value for the tropical year and was so succesful that it formed the basis of the calendar adopted in the Seleucid Empire (Mesopotamia) and was used in the Jewish calendar and the calendar of the Christian Church; it also influenced Indian astronomical teaching. The Metonic cycle was improved by both Callipus and Hipparchus. Calippus of Cyzius (c. 370-300 BC) was perhaps the foremost astronomer of his day. He formed what has been called the Callippic period, essentially a cycle of four Metonic periods. It was more accurate than the original Metonic cycle and made use of the fact that 365.25 days is a more precise value for the tropical year than 365 days. The Callippic period consisted of 4 x 235, or 940 lunar months, but its distribution of hollow and full months was different from Meton's. Instead of having totals of 440 hollow and 500 full months, Callippus adopted 441 hollow and 499 full, thus reducing the length of four Metonic cycles by one day. The total days involved therefore became (441x29) + (499x30), or 27,759 and 27,759 / (19x4) gives 365.25 days exactly. Thus the Callippic cycle fitted 940 lunar months precisely to 76 tropical years of 365.25 days. Hipparchus, who flourished in Rhodes about 150 BC and was probably the greatest observational astronomer of antiquity, discovered from his own observations and those of others made over the previous 150 years that the equinoxes, where the ecliptic (the Sun's apparent path) crosses the celestial equator (the celestial equivalent of the terrestiral Equator), were not fixed in space but moved slowly in a westerly direction. The movement is small, amounting to no more thqan 2 degrees in 150 years, and it is known now as an important discovery because the tropical year is measured with reference to the equinoxes, and precession reduced the value accepted by Calippus. Hipparchus calculated the tropical year to have a length of 365.242 days, which was very close to the present 365.242199 days; he also computed the precise length of a lunation, using a "great year" of four Calippic cycles. He arrived at the value of 29.53058 days for a lunation, which, again, is comparable with the present-day figure, 29.53059 days. The calendar dating of historical events, and the determination of how many days have elapsed since some astronomical ot other occurence are difficult for a number of reasons. Leap years have to be inserted, but not always regularly, months have changed their lengths and new ones have been added from time to time, years have commenced on varying dates and their lengths have been computed in various ways. Since historical dating must take all these factors into account, it occured to the 16th-century French classicist and literary scholar Joseph Justus Scaliger (1540-1609) that a consecutive numbering system could be arranged as a cyclic period of great length and he worked out the system that is known as the Julian period, in honour of this father Julius Caesar Scaliger (1484- 1558). He published his proposals in Paris in 1583 under the title De Emendatione Temporum. The Julian period is a cycle of 7,890 years. It is based on the Metonic Cycle of 19 years, a "solar cycle" of 28 years, and the Indiction Cycle of 15 years. The so-called solar cycle was a period after which the days of the seven-day week repeated on the same dates. Since one year contains 52 weeks of seven days, plus one day, the days of the week would repeat every seven years were no leap to intervene. A Julian calendar (see below) leap year cycle is four years, therefore the days of the week repeat on the same dates every 4x7 = 28 years. The cycle of indiction was a fiscal, not an astronomical period. It first appears in tax receipts for Egypt in AD 303, and probably took its origin in a periodic 15-year taxation census that followed Diocletian's reconquest of Egypt in AD 297. By multiplying the Metonic, solar, and Indiction cycles together, Scaliger obtained his cycle of 7,890 years (19x29x15 = 7,890) as period of sufficient length to cover most previous and future historical dates required at any one time. Scaliger, tracing each of the three cycles back in time, found that all coincided in the year 4713 BC, on the Julian calendar reckoning. On the information available to him, he beleived this to be a date considerably before any historical events. He therefore set the beginning of the first Julian period at Jan. 1, 4713 BC. The years of the Julian period are not now used, but the day number is still used in astronomy and in preparing calendar tables, for it is the only record where days are free from combination into weeks and months. ** NOTE: The day number is called the Julian Day. In the Geophysical Year (1958), mainly on account of space research, the Julian Day was standardized as the universal time scale, simplifying its use by suppressing the first two places and moving the origin back to Greenwich midnight, but in such a way that there is now a full day's difference and the modified Julian Day (MJD) is 2,400,001 less than Scaliger's Julian Day. Examples: Mo 1 Jan 4713 BC 0000000 Scaliger Era Fr 18 Feb 3102 BC 0588466 Flood (Ind Kalyuga) Sa 1 Jan 1 AD 1721424 Christian Era Th 15 Jul 622 AD 1948439 Muslim Era Th 4 Oct 1582 AD 2299160 End Julian Cal in Rome Fr 15 Oct 1582 AD 2299161 Begin Greg Cal in Rome We 17 Nov 1858 AD 2400001 MJD=000000 A number of non-astronomical natural signs have also been used in determining the seasons. In the Mediterranean area, such indications change rapidly, and Hesiod (c. 800 BC) mentions a wide variety: the cry of migrating cranes, which indicated a time for plowing and sowing; the time when snails climb up plants, after which digging in vineyards should cease; and so on. An unwitting approximation to the tropical year may also be obtained by intercalation, using a simple lunar calendar and observations of animal behaviour. Such an unusual situation has grown up among the Yami fishermen of Botel-Tobago Island, near Taiwan. They use a calendar based on phases of the Moon, and some time about March (the precise date depends on the degree of error of their lunar calendar compared with the tropical year) they go out in boats with lighted flares. If flying fish appear, the fishing season is allowed to commence, but if the lunar calendar is too far out of step with the seasons, the flying fish will not rise. Fishing is then postponed for another lunation, which they insert in the lunar calendar, thus having a year of 13 instead of the usual 12 lunations. THE EARLY ROMAN CALENDAR ------------------------ This originated as a local calendar in the city of Rome, supposedly drawn up by Romulus some seven or eight centuries BC. The year began in March and consisted of ten months, six of 30 days and four of 31 days, making a total of 304 days: it ended in December, to be followed by what seems to have been an uncounted winter gap. Numa Pompilius, traditionally the second king of Rome (715?-673? BC) is supposed to have added two extra months, January and February, to fill the gap and to have increased the total numer of days by 50, making 354. To obtain sufficient days for his new months, he is then said to have deducted one day from the 30-day months, thus having 56 days to divide between January and February. But since the Romans had, or had developed, a superstitious dread of even numbers, January was given an extra day; February was still left with an even number of days, but as that month was given over to the infernal gods, this was considered appropriate. The system allowed the year of 12 months to have 355 days, an uneven number. The so-called Roman Republican calendar was supposedly introduced by the Etruscan Tarquinius Priscius (616-579 BC), traditionally the fifth king of Rome. He wanted the year to begin in January since it contained the festival of the god of gates (later the god of all beginnings), but expulsion of the Etruscan dynasty in 510 BC led to this particular reform being dropped. The Roman Republican calendar still contained only 355 days, with February having 28 days; March, May, Quintilis (July) and October 31 days each; January, April, June, Sextilis (August), September, November, and December 29 days. It was basically a lunar calendar and short by 10 1/4 days of a 365 1/4-day tropical year, so in order to prevent it from becoming too far out of step with the seasons, an intercalary month, Intercalans, or Mercedonius (from merces meaning wages, since workmen were paid at this time of year), was inserted between February 23 and 24. It consisted of 27 or 28 days and was added once every two years; and in historical times at least, the remaining five days of February were omitted. The intercalation was therefore equivalent to an additional 22 or 23 days, so that in a four-year period the total days in the calendar amounted to (4x355) + 22 + 23, or 1,465: this gave an average of 366.25 days per year. Intercalation was the duty of the Pontifices, a board that assisted the chief magistrate in his sacrificial functions. The reasons for their decisions were kept secret, but because of some negligence and a measure of ignorance and corruption, the intercalations were irregular, and seasonal chaos resulted. In spite of this and the fact that it was over a day too long compared with the tropical year, much of the modified Roman Republican calendar was carried over into the Gregorian calendar now in general use. THE JEWISH CALENDAR ------------------- The structure of the calendar. The Jewish calendar in use today is lunisolar, the years being solar and the months lunar, but it also allows for a week of seven days. Because the year exceeds 12 lunar months by about 11 days, a 13th month of 30 days is intercalated in the third, sixth, eight, 11th, 14th, 17th, and 19th years of a 19-year cycle. Arrangements akin to this procedure are well attested in ancient Babylon. Among the Jews, however, a regular sequence of intercalation in fixed intervals is stated in the sources to have been introduced as late as the 4th century of the Chrisitan Era and dates from the period of Exile. For practical purposes - e.g., for reckoning the commencement of sabbaths - the day begins at sunset; but the calendar day of 24 hours always begins at 6 PM. The hour is divided into 1,080 parts (halaqim; this division is originally Babylonian), each part (heleq) equalling 3 1/3 seconds. The heleq is further divided into 76 rega'im. The synodic month is the average interval between two mean conjunctions of the Sun and Moon, when these bodies are as near as possible in the sky, which is reckoned at 29 days 12 hours 44 minutes 3 1/3 seconds; a conjunction is called a molad. This is also a Babylonian value. In the calendar month, however, only complete days are reckoned, the "full" month containing 30 days and the "defective" month 29 days. The months Nisan, Sivan (Siwan), Av, Tishri, Shevat, Tammuz, Elul, Tevet, and Adar (known as Second Adar, or Adar Sheni, in a leap year) are always defective, while Heshvan (Heshwan) and Kislev (Kislew) vary. The calendar, thus, is schematic and independant of the true New Moon. The number of days in a year varies. The number of days in a synodic month multiplied by 12 in a common year and by 13 in a leap year would yield fractional figures. Hence, again reckoning complete days only, the common year has 353, 354, or 355 days and the leap year 383, 384, or 385 days. A year in which both Heshvan and Kislev are full, called complete (shelema), has 355 of (if a leap year) 385 days; a normal (sedura) year, in which Heshvan is defective and Kislev full, has 354 or 384 days; while a defective (hasera) year, in which both these months are defective, has 353 or 383 days. ** NOTE: The length of the months in the 6 types of years: C o m m o n year L e a p year normal short long normal short long Tishri 30 30 30 30 30 30 Heschvan 29 29 30 29 29 30 Kislev 30 29 30 30 29 30 Tevet 29 29 29 29 29 29 Shevat 30 30 30 30 30 30 Adar 29 29 29 30 30 30 ve-Adar -- -- -- 29 29 29 Nisan 30 30 30 30 30 30 Iyyar 29 29 29 29 29 29 Sivan 30 30 30 30 30 30 Tammuz 29 29 29 29 29 29 Av 30 30 30 30 30 30 Elul 29 29 29 29 29 29 ===== ===== ===== ===== ===== ===== 354 353 355 384 383 385 The character of a year (quvi'a, literary "fixing") is described by three Hebrew letters, the first and third giving, respectively, the days of the weeks on which the New Year occurs and Passover begins, while the second is the initial of the Hebrew word for defective, normal, or complete. There are 14 types of qevi'ot, seven in common and seven in leap years. The New Year begins on Tishri 1, which may be the day of the molad of Tishri but is often delayed by one or two days for various reasons. Thus, in order to prevent the Day of Atonement (Tishri 10) from falling on a Friday or a Sunday and the seventh day of Tabernacles (Tishri 21) from falling on a Saturday, the new year must avoid commencing on Sundays, Wednesdays, or Fridays. Again, if the molad of Tishri occurs at noon or later, the new year is delayed by one or, if this would cause it to fall as above, two days. These dalays (dehuyyot) necessitate, by reason of the above-mentioned limits on the number of days in the year, two other delays. The mean beginning of the four seasons is called tequfa (literally "orbit", or "course"); the tequfa of Nisan denotes the mean Sun at the vernal equinox, that of Tammuz the mean Sun at the summer solstice, that of Tishri the mean Sun at the autumn equinox, and that of Tevet the mean Sun at the winter solstice. As 52 weeks are the equivalent to 364 days, and the length of the solar year is nearly 365 1/4 days, the tequfot move forward in the week by about 1 1/4 days each year. Accordingly, reckoning the length of the year at the approximate value of 365 1/4 days, they are held to revert after 28 years (28 x 1 1/4 = 35 days) to the same hour on the same day of the week (Tuesday, 6 PM) as the beginning. This cycle is called the great, or solar, cycle (mahzor gadol or hamma). The present Jewish calendar is mainly based on the more accurate value 365 days, five hours, 55 minutes, 25 25/57 seconds - in exces of the true tropical year by about 6 minutes, 40 seconds. Thus, it is advanced by one day in about 228 years with regard to the equinox. To a far greater extent than the solar cycle of 28 years, the Jewish calendar employs, as mentioned above, a small, or lunar, cycle (mahzor qatan) of 19 years, adjusting the lunar months to the solar years by intercalations. Passover, on Nisan 15, is not to begin before the spring tequfa, and so the intercalary month is added after Adar. The mahzor qatan is akin to the Metonic cycle, a 19-year cycle proposed by the Athenian astronomer Meton in about 432 BC in which seven months were intercalated, and is based on the nearly correct notion that 235 lunar months are equal to 19 solar years. As, however, 19 "years", of 12 lunar months contain only 228 lunar months, seven intercalations are needed at the intervals set forth above in a 19-year cycle to bring it up to the required 235 months. The Jewish Era in use today is that dated from the supposed year ot the Creation (designated annu mundi or AM) with its epoch, or beginning, in 3752 BC. The Jewish year 5735 AM, the 16th in the 302nd lunar cycle and the 23rd in the 205th solar cycle, is a regular year of 12 months, or 354 days. The qevia is, using the three respective letters of the Hebrew alphabet as two numerals and an initial in the manner indicated in the second paragraph above, GKH, which indicates that Rosh Hashana (New Year) begins on the third (G=3) and Passover on the fifth (H=5) day of the week and that the year is regular (K=ke-sidra); i.e., Heshvan is defective - 29 days, and Kislev full - 30 days. The Jewish year (1974-75 of the Christian Era) begins September 17, 1974, and ends September 5, 1975. Neglecting the thousands, current Jewish years AM are converted into years of the current Christian Era by adding 239 of 240 - 239 from the Jewish New Year (about September) ot December 31 and 240 from January 1 to the eve of the Jewish New Year. The adjustment differs slightly for the conversion if dates of now-antiquated versions of the Jewish Era of the Creation and the Christian Era, or both. Tables for the exact conversions of such dates are available. Months and important days. The months of the Jewish year and the notable days are as follows: Tishri: 1-2, Rosh Hashana (New Year); 3, Fast of Gedaliah; 10, Yom Kippur (Day of Atonement); 15-21, Sukkot (Tabernacles); 22, Shemini Atzeret (eight Day of Solemn Assembly); 23, Simhat Torah (Rejoicing of the Law). Heshvan. Kislev: 25, Hanukka (Festival of Lights) begins. Tevet: 2 or 3, Hanukka ends; 10, Fast. Shevat: 15, New Year for Trees (Mishna). Adar: 13, Fast of Esther; 14-15, Purim (Lots). Second Adar (Adar Sheni) or ve-Adar (intercalated month); Adar holidays fall in ve-Adar during leap years. Nisan: 15-22, Pesah (Passover) Iyyar: 5, Israel Independence Day. Sivan: 6-7, Shavuot (Feast of Weeks [Pentecost]). Tammuz: 17, Fast (mishna). Av: 9, fast (Mishna). Elul. The calendar in Jewish history. For the months of the Jewish year and the notable days of the Jewish calendar see JEWISH RELIGIOUS YEAR. Present knowledge of the pre-exilic Jewish calendar is both limited and uncertain. The Bible refers to calendar matters only incidentally, and the dating of components of Mosaic Law remains doubtful. The earliest datable source for the Hebrew calendar is the Gezer Calendar, written probably in the age of Solomon, in the late 10th century BC. The inscription indicates the length of main agricultural tasks within the cycle of 12 lunations. The calendar term here is yereah, which in Hebrew denotes both "moon" and "month". The second Hebrew term for month, hodesh properly means the "newness" of the lunar crescent. Thus, the Hebrew months were lunar. They are not named in pre-exilic sources except in the biblical report of the building of Solomon's Temple in I kings, where the names of three months, two of them also attested in the Phoenician calendar, are given; the months are usually numbered rather than named. The "beginning of the months" was the month of the Passover. In some passages, the Passover month is that of hodesh ha-aviv, the lunation that coincides with the barley being in the ear. Thus, the Hebrew calendar is tied in with the course of the Sun, that determines ripening of the grain. It is not known how the lunar year of 354 days was adjusted to the Sun year of 365 days. The Bible never mentions intercalation. The year shana, properly "change" (of seasons), was the agricultural and, thus, liturgical year. There is no reference to the New Year's day in the Bible. After the conquest of Jerusalem (587 BC), the Babylonians introduced their cyclic calendar and the reckoning of their regnal years from Nisanu 1, about the spring equinox. The Jews now had a finite calendar year with a New Year's day, and they adopted the Babylonian month names, which they continue to use. >From 587 BC until AD 70, the Jewish civil year was Babylonian, except for the period of Alexander the Great and the Ptolemies (332-200 BC), when the Macedonian calendar was used. The situation after the destruction of the Temple in Jerusalem in AD 70 remains unclear. It is not known wether the Romans introduced their Julian calendar or the calendar that the Jews of Palestine used after AD 70 for their business transactions. There is no calendar reference in the New Testament; the contemporary Aramaic documents from Judaea are rare and prove only that the Jews dated events according to the years of the Roman emperors. The abundant data in the Talmudic sources concern only the religious calendar.