History
Basic chronology in the biblical period
From very early times, the Babylonian calendar was in wide use by the countries of the Near East. The structure, which was also used by theMonth names
Biblical references to thePast methods of dividing years
According to some Christian and Karaite sources, the tradition in ancient Israel was that 1 Nisan would not start until the barley is ripe, being the test for the onset of spring. If the barley was not ripe, an intercalary month would be added before Nisan. In the 1st century,Moses...appointed Nisan...as the first month for the festivals...the commencement of the year for everything relating to divine worship, but for selling and buying and other ordinary affairs he preserved the ancient order . e. the year beginning with Tishrei"Josephus, ''Antiquities'' 1.81, Loeb Classical Library, 1930.
Past methods of numbering years
Before the adoption of the current ''Anno Mundi'' year numbering system, other systems were used. In early times, the years were counted from some significant event such asThe use of the era of documents (i.e., Seleucid era) continued till the 16th century in the East, and was employed even in the 19th century among the Jews of Yemen. Occasionally in Talmudic writings, reference was made to other starting points for eras, such as destruction era dating,Avodah Zarah 9aRav ''Rav'' (or ''Rab,'' Modern Hebrew: ) is the Hebrew generic term for a person who teaches Torah; a Jewish spiritual guide; or a rabbi. For example, Pirkei Avot (1:6) states that: The term ''rav'' is also Hebrew for ''rabbi''. (For a more nuan ...Aha bar Jacob then put this question: How do we know that our Era f Documentsis connected with the Kingdom of Greece at all? Why not say that it is reckoned from the Exodus from Egypt, omitting the first thousand years and giving the years of the next thousand? In that case, the document is really post-dated!
Said Rav Nahman: In the Diaspora the Greek Era alone is used.
Heav Aha Av (also Menachem Av, ; from Akkadian ''ʾAbū'' "father") is the eleventh month of the civil year and the fifth month of the ecclesiastical year on the Hebrew calendar. The name comes from Araḫ Abu, "month of Abu", from the Babylonian calenda ...thought that Rav Nahman wanted to dispose of him anyhow, but when he went and studied it thoroughly he found that it is indeed taught n a Baraita">Baraita.html" ;"title="n a Baraita">n a Baraita In the Diaspora the Greek Era alone is used.
Leap months
When the observational form of the calendar was in use, whether or not an embolismic month was announced after the "last month" (Determining the new month in the Mishnaic period
TheThe fixing of the calendar
Between 70 and 1178 CE, the observation-based calendar was gradually replaced by a mathematically calculated one. The Talmuds indicate at least the beginnings of a transition from a purely empirical to a computed calendar. Samuel of Nehardea (c. 165-254) stated that he could determine the dates of the holidays by calculation rather than observation. According to a statement attributed to Yose (late 3rd century),Components
Days
Based on the classic rabbinic interpretation of ("There was evening and there was morning, one day"), a day in the rabbinic Hebrew calendar runs from sunset (the start of "the evening") to the next sunset. The same definition appears in the Bible in Leviticus 23:32, where the holiday ofHours
Judaism uses multiple systems for dividing hours. In one system, the 24-hour day is divided into fixed hours equal to of a day, while each hour is divided into 1080 ''halakim'' (parts, singular: '' helek''). A part is seconds ( minute). The ultimate ancestor of the ''helek'' was a small Babylonian time period called a ''barleycorn'', itself equal to of a Babylonian ''time degree'' (1° of celestial rotation).Otto Neugebauer, "The astronomy of Maimonides and its sources", ''Hebrew Union College Annual'' 23 (1949) 322–363. These measures are not generally used for everyday purposes. Its best known use is for calculating and announcing the molad. In another system, the daytime period is divided into 12 relative hours (''sha'ah z'manit'', also sometimes called "halachic hours"). A relative hour is defined as of the time from sunrise to sunset, or dawn to dusk, as per the two opinions in this regard. Therefore an hour can be less than 60 minutes in winter, and more than 60 minutes in summer; similarly, the 6th hour ends at solar noon, which generally differs from 12:00. Relative hours are used for the calculation of prayer times (Weeks
The Hebrew week (, ) is a cycle of seven days, mirroring the seven-day period of theNames of weekdays
The names for the days of the week are simply the day number within the week, withDays of week of holidays
The period from 1Months
The Hebrew calendar is aJustification for leap months
The insertion of the leap month mentioned above is based on the requirement thatBy how much does the solar year exceed the lunar year? By approximately 11 days. Therefore, whenever this excess accumulates to about 30 days, or a little more or less, one month is added and the particular year is made to consist of 13 months, and this is the so-called embolismic (intercalated) year. For the year could not consist of twelve months plus so-and-so many days, since it is said: throughout the months of the year, which implies that we should count the year by months and not by days.The Bible does not directly mention the addition of "embolismic" or intercalary months. However, without the insertion of embolismic months, Jewish festivals would gradually shift outside of theMishneh Torah The ''Mishneh Torah'' ( he, מִשְׁנֵה תּוֹרָה, , repetition of the Torah), also known as ''Sefer Yad ha-Hazaka'' ( he, ספר יד החזקה, , book of the strong hand, label=none), is a code of Rabbinic Jewish religious law (''h ..., Sanctification of the New Moon 1:2; quoted i
Sanctification of the New Moon
. Translated from the Hebrew by Solomon Gandz; supplemented, introduced, and edited by Julian Obermann; with an astronomical commentary by Otto Neugebauer. Yale Judaica Series, Volume 11, New Haven: Yale University Press, 1956.
Characteristics of leap months
In a regular (''kesidran'') year, Marcheshvan has 29 days and Kislev has 30 days. However, because of the Rosh Hashanah postponement rules (see below) Kislev may lose a day to have 29 days, and the year is called a short (''chaser'') year, or Marcheshvan may acquire an additional day to have 30 days, and the year is called a full (''maleh'') year. The calendar rules have been designed to ensure that Rosh Hashanah does not fall on a Sunday, Wednesday or Friday. This is to ensure thatYears
The Hebrew calendar year conventionally begins onAnno Mundi
In 1178 CE,New year
The Jewish calendar has several distinct new years, used for different purposes. The use of multiple starting dates for a year is comparable to different starting dates for civil "calendar years", "tax orThe 1st of Nisan is the new year for kings and festivals; the 1st of Elul is the new year for the cattle tithe... the 1st of Tishri is the new year for years, of the years of release and Jubilee years, for the planting and for vegetables; and the 1st ofTwo of these dates are especially prominent: * 1 Nisan is the ''ecclesiastical new year'', i.e. the date from which months and festivals are counted. ThusShevat Shevat (Hebrew: שְׁבָט, Standard ''Šəvaṭ'', Tiberian ''Šeḇāṭ''; from Akkadian ''Šabātu'') is the fifth month of the civil year starting in Tishre (or Tishri) and the eleventh month of the ecclesiastical year on the Hebrew calend ...is the new year for trees—so the school of Shammai; and the school of Hillel say: On the 15th thereof.
Leap years
The Jewish calendar is based on theRosh Hashanah postponement rules
To calculate the day on which Rosh Hashanah of a given year will fall, it is necessary first to calculate the expected molad (moment ofDeficient, regular, and complete years
The postponement of the year is compensated for by adding a day to the second month or removing one from the third month. A Jewish common year can only have 353, 354, or 355 days. A leap year is always 30 days longer, and so can have 383, 384, or 385 days. *A year (Hebrew for "deficient" or "incomplete") is 353 or 383 days long. Both Cheshvan and Kislev have 29 days. The Hebrew letter ח "het" is used in the . *A year ("regular" or "in-order") is 354 or 384 days long. Cheshvan has 29 days while Kislev has 30 days. The Hebrew letter כ "kaf" is used in the ''keviyah''. *A year ("complete" or "perfect", also "abundant") is 355 or 385 days long. Both Cheshvan and Kislev have 30 days. The Hebrew letter ש "shin" is used in the ''keviyah''. Whether a year is deficient, regular, or complete is determined by the time between two adjacent Rosh Hashanah observances and the leap year. While the is sufficient to describe a year, a variant specifies the day of the week for the first day of Pesach (Four gates
The annual calendar of a numbered Hebrew year, displayed as 12 or 13 months partitioned into weeks, can be determined by consulting the table of Four gates, whose inputs are the year's position in the 19-year cycle and its molad Tishrei. The resulting type () of the desired year in the body of the table is a triple consisting of two numbers and a letter (written left-to-right in English). The left number of each triple is the day of the week of , Rosh Hashanah ; the letter indicates whether that year is deficient (D), regular (R), or complete (C), the number of days in Chesvan and Kislev; while the right number of each triple is the day of the week of , the first day of Passover or Pesach , within the same Hebrew year (next Julian/Gregorian year). The in Hebrew letters are written right-to-left, so their days of the week are reversed, the right number for and the left for . The year within the 19-year cycle alone determines whether that year has one or two Adars. This table numbers the days of the week and hours for the limits of molad Tishrei in the Hebrew manner for calendrical calculations, that is, both begin at , thus is noon Saturday. The years of a 19-year cycle are organized into four groups: common years after a leap year but before a common year ; common years between two leap years ; common years after a common year but before a leap year ; and leap years , all between common years. The oldest surviving table of Four gates was written by Muhammad ibn Musa al-Khwarizmi inHolidays
See Jewish and Israeli holidays 2000–2050Other calendars
Outside ofKaraite calendar
Karaites use the lunar month and the solar year, but the Karaite calendar differs from the current Rabbinic calendar in a number of ways. The Karaite calendar is identical to the Rabbinic calendar used before the Sanhedrin changed the Rabbinic calendar from the lunar, observation based, calendar to the current, mathematically based, calendar used in Rabbinic Judaism today. In the lunar Karaite calendar, the beginning of each month, the Rosh Chodesh, can be calculated, but is confirmed by the observation inSamaritan calendar
The Samaritan community's calendar also relies on lunar months and solar years. Calculation of the Samaritan calendar has historically been a secret reserved to the priestly family alone, and was based on observations of the new crescent moon. More recently, a 20th-century Samaritan High Priest transferred the calculation to a computer algorithm. The current High Priest confirms the results twice a year, and then distributes calendars to the community. The epoch of the Samaritan calendar is year of the entry of theThe Qumran calendar
Many of theOther calendars used by ancient Jews
Calendrical evidence for the postexilic Persian period is found inAstronomical calculations
Synodic month – the molad interval
A "Seasonal drift
The mean year of the current mathematically based Hebrew calendar is 365 days 5 hours 55 minutes and 25+25/57 seconds (365.2468 days) – computed as the molad/monthly interval of 29.530594 days × 235 months in a 19-year metonic cycle ÷ 19 years per cycle. In relation to theImplications for Jewish ritual
Although the molad of Tishrei is the only molad moment that is not ritually announced, it is actually the only one that is relevant to the Hebrew calendar, for it determines the provisional date of Rosh Hashanah, subject to the Rosh Hashanah postponement rules. The other monthly molad moments are announced for mystical reasons. With the moladot on average almost 100 minutes late, this means that the molad of Tishrei lands one day later than it ought to in (100 minutes) ÷ (1440 minutes per day) = 5 of 72 years or nearly 7% of years. Therefore, the seemingly small drift of the moladot is already significant enough to affect the date of Rosh Hashanah, which then cascades to many other dates in the calendar year and sometimes, due to the Rosh Hashanah postponement rules, also interacts with the dates of the prior or next year. The molad drift could be corrected by using a progressively shorter molad interval that corresponds to the actual mean lunar conjunction interval at the original molad reference meridian. Furthermore, the molad interval determines the calendar mean year, so using a progressively shorter molad interval would help correct the excessive length of the Hebrew calendar mean year, as well as helping it to "hold onto" the northward equinox for the maximum duration. When the 19-year intercalary cycle was finalised in the 4th century, the earliest Passover (in year 16 of the cycle) coincided with the northward equinox, which means that Passover fell near the ''first'' full moon after the northward equinox, or that the northward equinox landed within one lunation before 16 days after the ''molad'' of ''Nisan''. This is still the case in about 80% of years; but, in about 20% of years, Passover is a month late by these criteria (as it was in AM 5765, 5768 and 5776, the 8th, 11th and 19th years of the 19-year cycle = Gregorian 2005, 2008 and 2016 CE). Presently, this occurs after the "premature" insertion of a leap month in years 8, 11, and 19 of each 19-year cycle, which causes the northward equinox to land on exceptionally early Hebrew dates in such years. This problem will get worse over time, and so beginning in AM 5817 (2057 CE), year 3 of each 19-year cycle will also be a month late. If the calendar is not amended, then Passover will start to land on or after the summer solstice around AM 16652 (12892 CE). In theory, the exact year when this will begin to occur depends on uncertainties in the future tidal slowing of the Earth rotation rate, and on the accuracy of predictions of precession and Earth axial tilt. The seriousness of the spring equinox drift is widely discounted on the grounds that Passover will remain in the spring season for many millennia, and the text of the Torah is generally not interpreted as having specified tight calendrical limits. The Hebrew calendar also drifts with respect to the autumn equinox, and at least part of the harvest festival of Sukkot is already more than a month after the equinox in years 1, 9, and 12 of each 19-year cycle; beginning in AM 5818 (2057 CE), this will also be the case in year 4. (These are the same year numbers as were mentioned for the spring season in the previous paragraph, except that they get incremented at Rosh Hashanah.) This progressively increases the probability that Sukkot will be cold and wet, making it uncomfortable or impractical to dwell in the traditional ''succah'' during Sukkot. The first winter seasonal prayer for rain is not recited until ''Shemini Atzeret'', after the end of Sukkot, yet it is becoming increasingly likely that the rainy season in Israel will start before the end of Sukkot. No equinox or solstice will ever be more than a day or so away from its mean date according to the solar calendar, while nineteen Jewish years average 6939d 16h 33m 03s compared to the 6939d 14h 26m 15s of nineteen mean tropical years. This discrepancy has amounted to six days, which is why the earliest Passover currently falls on 26 March (as in AM 5773 / 2013 CE).Worked example
Given the length of the year, the length of each month is fixed as described above, so the real problem in determining the calendar for a year is determining the number of days in the year. In the modern calendar, this is determined in the following manner. The day of Rosh Hashanah and the length of the year are determined by the time and the day of the week of the Tishrei ''molad'', that is, the moment of the average conjunction. Given the Tishrei ''molad'' of a certain year, the length of the year is determined as follows: First, one must determine whether each year is an ordinary or leap year by its position in the 19-year Metonic cycle. Years 3, 6, 8, 11, 14, 17, and 19 are leap years. Secondly, one must determine the number of days between the starting Tishrei ''molad'' (TM1) and the Tishrei ''molad'' of the next year (TM2). For calendar descriptions in general the day begins at 6 p.m., but for the purpose of determining Rosh Hashanah, a ''molad'' occurring on or after noon is treated as belonging to the next day (the first ''deḥiyyah''). All months are calculated as 29d, 12h, 44m, 3s long (MonLen). Therefore, in an ordinary year TM2 occurs 12 × MonLen days after TM1. This is usually 354 calendar days after TM1, but if TM1 is on or after 3:11:20 a.m. and before noon, it will be 355 days. Similarly, in a leap year, TM2 occurs 13 × MonLen days after TM1. This is usually 384 days after TM1, but if TM1 is on or after noon and before 2:27:16 p.m., TM2 will be only 383 days after TM1. In the same way, from TM2 one calculates TM3. Thus the four natural year lengths are 354, 355, 383, and 384 days. However, because of the holiday rules, Rosh Hashanah cannot fall on a Sunday, Wednesday, or Friday, so if TM2 is one of those days, Rosh Hashanah in year 2 is postponed by adding one day to year 1 (the second ''deḥiyyah''). To compensate, one day is subtracted from year 2. It is to allow for these adjustments that the system allows 385-day years (long leap) and 353-day years (short ordinary) besides the four natural year lengths. But how can year 1 be lengthened if it is already a long ordinary year of 355 days or year 2 be shortened if it is a short leap year of 383 days? That is why the third and fourth ''deḥiyyah''s are needed. If year 1 is already a long ordinary year of 355 days, there will be a problem if TM1 is on a Tuesday, as that means TM2 falls on a Sunday and will have to be postponed, creating a 356-day year. In this case, Rosh Hashanah in year 1 is postponed from Tuesday (the third ''deḥiyyah''). As it cannot be postponed to Wednesday, it is postponed to Thursday, and year 1 ends up with 354 days. On the other hand, if year 2 is already a short year of 383 days, there will be a problem if TM2 is on a Wednesday. because Rosh Hashanah in year 2 will have to be postponed from Wednesday to Thursday and this will cause year 2 to be only 382 days long. In this case, year 2 is extended by one day by postponing Rosh Hashanah in year 3 from Monday to Tuesday (the fourth ''deḥiyyah''), and year 2 will have 383 days.Rectifying the Hebrew calendar
Given the importance in Jewish ritual of establishing the accurate timing of monthly and annual times, some futurist writers and researchers have considered whether a "corrected" system of establishing the Hebrew date is required. The mean year of the current mathematically based Hebrew calendar has "drifted" an average of 7–8 days late relative to the equinox relationship that it originally had. It is not possible, however, for any individual Hebrew date to be a week or more "late", because Hebrew months always begin within a day or two of the '' molad'' moment. What happens instead is that the traditional Hebrew calendar "prematurely" inserts a leap month one year before it "should have been" inserted, where "prematurely" means that the insertion causes the spring equinox to land more than 30 days before the latest acceptable moment, thus causing the calendar to run "one month late" until the time when the leap month "should have been" inserted prior to the following spring. This presently happens in 4 years out of every 19-year cycle (years 3, 8, 11, and 19), implying that the Hebrew calendar currently runs "one month late" more than 21% of the time. Dr. Irv Bromberg has proposed a 353-year cycle of 4,366 months, which would include 130 leap months, along with use of a progressively shorter ''molad'' interval, which would keep an amended fixed arithmetic Hebrew calendar from drifting for more than seven millennia. It takes about 3 centuries for the spring equinox to drift an average of th of a ''molad'' interval earlier in the Hebrew calendar. That is a very important time unit, because it can be cancelled by simply truncating a 19-year cycle to 11 years, omitting 8 years including three leap years from the sequence. That is the essential feature of the 353-year leap cycle. (). Another suggestion is to delay theCalendar observance in Auschwitz
While imprisoned inUsage in contemporary Israel
EarlySee also
* Biblical and Talmudic units of measurement * Chronology of the Bible * Gezer calendar *Notes
References
Bibliography
* al-BiruniExternal links
Date converters