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The Hebrew Calendar (in a nutshell)
THE HEBREW CALENDAR (in a nutshell)
The Hebrew calendar is based, primarily, on the moon's rotation, or what is known as the lunar calendar, consisting of twelve lunar months. Each lunar month is made-up of exactly 29 days, 12 hours and 44 minutes.[1] These numbers collected altogether amount to 354 days to each year, or what is known as "a regular year" (Heb. כסדרה), while the accumulation of 44 minutes to each lunar month amounts to nearly 9 hours in the course of a year; in two years, to nearly 18 hours, and in three years, to a little more than 26 hours, or what can be termed as an additional day. It is therefore necessary to make the addition of one 24-hour day every three years to the Hebrew calendar, turning an ordinary 29-day lunar month of Heshwan into a 30-day month, or what is known as an intercalated month, and which brings the Jewish year to 355 days. Such a year is called "a full year" (Heb. שלמה). Now since each lunar month repeats its phases, or starts anew with the mean conjunction of the sun (hence: New Moon) every 29 1/2 days, and since, for all practical purposes, it is impossible to divide a day in half, this accounts for why the twelve lunar months in the Jewish calendar are made-up of 30, 29, 30, 29, etc. days respectively, which balances out in the long run.[2] The first of these lunar months is Nisan, as it is written (Exo. 12:2): "This month shall be unto you the beginning of months." It is made-up of 30-days.
Note that there is a difference of eleven days between a Solar Year (of 365 days) and a Lunar Year (of 354 days). The Seasons repeat themselves every twelve months. However, the seasons are governed by the earth's rotation around the sun (i.e. Solar Year) of 365 days, rather than by the moon's rotation. Here, a technical problem arises insomuch that Passover, according to a biblical injunction (Deut. 16:1), must always fall in the springtime. Since the lunar year lags behind the solar year by eleven days each year, and after three years it would lag behind the solar year by 33 days, had this process continued, Passover would have eventually fallen in the winter months. It, therefore, becomes necessary to intercalate the year by adding another month to the Hebrew calendar every two or three years, in order to keep the lunar cycle aligned with the solar cycle.[3] This accounts for the first and second months of Adar which are added to the calendar in a Leap Year (Heb. שנה מעוברת), there being seven Leap Years in the course of a nineteen-year period. These Leap Years are repeated in their regular order every 19 years. The first Adar is always a 30-day month, while the second Adar is always a 29-day month. As for the three surplus days in the 33-day lag every three years and which were not accounted for by the addition of a 30-day month, these days are taken in by the frequencies of Leap Years occurring every 2 to 3 years (seven in a 19-year period), so that in 19 years, 210 days have been added to the Hebrew calendar by the addition of a 30-day month, making the total number of days equal to the total number of days appearing in a 19-year Solar Year (6,935 days). Complete alignment of the Solar and Lunar years are attained every 19 years, while in between these years, the two are constantly running in close proximity to each other.
The Hebrew months, in their proper order, are as follows:
Nisan = 30 days
Iyyar = 29 days
Siwan = 30 days
Tammuz = 29 days
Av = 30 days
Elul = 29 days
Tishri = 30 days
Heshwan = 29 days (30 days when intercalated, making it "a full year")
Kisleu = 30 days (29 days in "a defective year")
Tevet = 29 days
Shevat = 30 days
Adar = 29 days (In a Leap Year, the first Adar is 30 days)
FOOTNOTE:
[1] In ancient times, the sages of Israel had different ways of expressing the time, or duration, of the lunar month, or what is sometimes called the "mean lunation." In the Babylonian Talmud (Rosh Hashanah 25a), is written: "Rabban Gamliel said to them, 'Thus have I received it as a tradition from my grandfather's family that the mean lunation is no more than 29-days, and a half-day, and two-thirds of an hour, and 73 parts, ' etc."
[2] Formerly, each new lunar month was sanctified by the testimony of eye witnesses who had seen it appear in the sky.
[3] cf. Babylonian Talmud (Rosh Hashanah 21a); Maimonides (Mishne Torah, H. Kiddush Ha-Chodesh 4:1; 1:1-2)
Tags: Calendar, Chodesh, Intercalation, Leap-Year, Lunar-year, New-moon
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The Exilarch's Lettter
The Cambridge University library in England houses an invaluable document taken from the Cairo Geniza (TS 8 G71), or what has now come to be known as "the Exilarch's letter." The letter, inscribed in Aramaic and dated 835/6 CE, proposes to the Court in the land of Israel that certain emendations be made to the calendar in the forthcoming year, in keeping with the "rules of postponement," which rules prohibit having the 1st of Tishri (New Year's Day) fall on either a Sunday, Wednesday or Friday due to the inconvenience that it would cause down the line, during the upcoming feasts and solemn days. The Exilarch David ben Yehudah is believed to have sent this letter, seeking the approval of the Court in the land of Israel. Since olden days, the Babylonian Jews had been accustomed to this practice of "postponement." Presumably, after having made the necessary astronomical calculations, or algorithms, and after having made a rough draft of the calendar, the Exilarch presented his proposals to the sages in the land of Israel, seeking their ratification, seeing that only they were invested with the power and authority to intercalate the months and the years in the Hebrew calendar. The importance of this document was recognised by R. Joseph Mann, who brought it to the attention of the academic world in 1922.[1] It has since been printed in the portly volumes of "Otzar Hageonim," s.v. the Jewish New Year, p. 35; in the journal "Sinai," vol. 30, p. 121, and in Hatekufah Yad, p. 346, all of which are Hebrew works. An English description and translation of the document has been printed in Sacha Stern's "Calendar and Community, A History of the Jewish Calendar Second Century BCE," pp. 277-283. We offer, here, a new English translation. The Exilarch's proposals were accepted, and they became the standard practice in the land of Israel by the year 839 CE.
(ENGLISH TRANSLATION of the Exilarch's Letter)
Whereas all of us, and all those of Israel, might be of one partnership in the [fixation of all of the lunar] months and in all of the feasts, in accordance with this custom that our fathers and the academies have made a rule of practice [amongst us] until now, which year is anno 1,147 of the Seleucid Era (835/6 CE), the same year being 4,595 anno mundi, even though with respect to [the lunar months] Marahšewan, Kisleu and Teveth, [the appearance of] their moons will be delayed [by doing so], even so, because of the moon of Nisan whose mean conjunction (i.e. beginning of the New Moon) would [otherwise] start in the daytime of the of third [day] of the week (= Tuesday), at four hours, if we were to intercalate [these months of 835/6 CE] so that they became 'full' [months], the fixation of Nisan would then fall on the fifth [day of the week] (= Thursday) and would, [therefore], become visible before its fixation [had been known] in the West (= i.e. the land of Israel), thereby bringing into disorder some matter. Now had we left [these months] to their regular order, this, too, would have been impossible, for [in this case] Passover would have fallen out on the fourth day of the week (= Wednesday), whereas [we have a rule which proscribes the practice]: 'Passover is never to fall on a Monday, Wednesday and Friday.' [2] And why is it that Passover is never to fall on a Monday, Wednesday and Friday,[3] nor Pentecost (the Feast of Weeks) on a Tuesday, Thursday and Saturday? This is because the Jewish New Year (Heb. Rosh Hashanah) should never fall on a Sunday, Wednesday and Friday.[4] Now if we were to make Passover on the second day of the week (= Monday), New Year's Day (i.e. the 1st of Tishri) would have then fallen on the fourth [day] (= Wednesday), while the Day of Atonement on a Friday, which thing cannot be done on account of the dead.[5] Moreover, had we made Passover to fall on the fourth [day] (= Wednesday), New Year's Day (i.e. the 1st of Tishri) would have then fallen on a Friday, and the Day of Atonement on the first day of the week (= Sunday), which thing cannot be done on account of having to leave the dead unburied for the two sabbatical days of rest. So, too, if we had made Passover fall on a Friday, New Year's Day (i.e. the 1st of Tishri) would have then fallen on the first day of the week (= Sunday), which thing cannot be done on account of the grand festival day of the willow branch [twenty days later]; so that the [day of the] willow branch might not fall on a Sabbath.[6] Now there is nothing that we can do except to make the months defective on account of Nisan, so that the moon's [conjunction with the sun] might not be disrupted.
Has it not become necessary in this particular case, for thus was it performed of them when they had [brought?] the 'defective' [months] before the head of the panel of judges [7] [in the land of Israel], as well as the members of that panel, upon whom we rely, when we were unable [of ourselves] to make them 'regular' [months], neither 'full' [months]. Rather, even if we should have occasionally made them 'regular' and 'full' [months], or 'defective' [months], they all resembled one another! So it is that we rely upon them always (i.e. the Court in the land of Israel), so that Israel might not be broken-up into vying factions. Wherefore, I and the heads of the academy, as well as the Rabbis, and all of Israel, rely upon this calendar that was sent before our friends, excepting where it has been made known to me that there are a few [men] who fear G-d [and will not abrogate from the regular order, be what it might be].
(The Original Language of the Document)
...דלי הוי כולן וכל יש' אגודה [אחת בח]דשים וכל מועדים כבהדין מנהגא ק[א מ]דברין אבהתן ומתיבאתא עד הינא והי[א] שתה דהוה שנת אלפא ומאה וארבעין ושבע שנין לשטרות והיא שנת ארבעת אלפים וחמש מאות ותשעים וחמש שנים לבראשית אף על גב דילעינין מְרַחְשְׁוָן וכסליו וטבת מתאחר סהרא דילהון אפילו הכין משום סיהרא דניסן דקא מיתליד ביממא דתלתה בש[ב]ה בארבע [ש]עות אי מעברינן שלימ[י]ן האוי קבעיה דניסן בחמשה ומתחזי מן קמי קבעיה במערב ומיקלקל מידי ושוינין כסדרן לא איפשר דמיתרמי פסח בארבעה בשבה ולא בד"ו פסח ולמה לא ב[ד"ו] פסח ולא גה"ז עצרת משום לא אד"ו ראש השנה ואי עבדינן פסח בתר[ין ב]שבה מתרמיא ראש שתא בארבעה ו[יום כ]פור במעלי ולית איפ[שר משו]ם שכבה וא[י ע]בדינן פסח בארבעה [אתיא] ראש שתא [ב]מעל[י] ו[י]ום כפור בחד ב[ש]בה ולית איפשר משום שכבה למיבת תרי יומי דשבת שבתון ואי עבדינן פסח במעלי אתיא ראש שתא בחד בשבה ולית איפש[ר] משום יום טוב גדול של ערבה דלא ליתרמי ערבא בשבתא ולא סגיא אלא לשויינון לירחי חסירין משום ניסן דלא ליקלקל סיהרא.
ולא [מי]בעיא בהכי הדין מעשה דכ[דין] עבדו ו[שדרו?] לקמי ראש החבורה וב[ני] החבורה חסירין ד[ס]מכינן עליהון דלא איפשר לשויינון לא כסדרן ולא שלמין אלא אפילו זמנין דאי עבדינן כסדרן ושל[מין] או חסירין דאמי להדדי ולעולם עליהון סמכינן דלא ליהוי ישראל אגודות אגודות ואנא וראשי מתיבאתא ורבנין וכל יש' אממכנן (אולי צ"ל אסמיכנן) על עיבורא דאישתדר לקמי ח[ב]ירין. לבר. היכין דאמרו קמי אית קא דחלין מן שמיא
The Rules of Postponement (according to Maimonides)
The "rules of postponement" required that whenever men sat down and made astronomical calculations and algorithms for the intent of drawing up calendars for the upcoming years, whenever they saw that the 1st day of Tishri (New Year's Day) would have ordinarily fallen on a Sunday, Wednesday or Friday, the sanctification of the new lunar moon of Tishri (New Year's Day) was to be delayed by them till the 2nd of Tishri, whereby the previous lunar month, Elul, was then to be intercalated and made into a 30-day month, instead of a 29-day month. Maimonides (Mishne Torah, Hilkoth Qidush Hahodesh 6:1; 7:1) spells out the method of doing this:
[6:1] "During the time when they determined the new moon by visual observation, they (the Court) would make astronomical calculations and would know the [likely] hour in which would occur the conjunction of the moon with the sun, with precise and painstaking accuracy, just as the astrologers do in order to know whether or not the moon is about to appear. Now the principles used in making astronomical calculations which are calculated at a time when there is no Court to fix [the new moons] by way of visual observation, it happens to be the astronomical calculations which we make use of today, which is called a calendar…
[7:1] "They never fix the new moon of Tishri, by this calculation, on a Sunday, neither on a Wednesday, nor on a Friday. Their mnemonics are ADU (A = Sunday; D = Wednesday; U = Friday). Rather, whenever the conjunction of the moon with the sun falls on one of these three days, they fix the new moon on the day after. For example: Had the conjunction of the moon with the sun fallen on the first day of the week (= Sunday), the new moon of Tishri is fixed on the second day (= Monday); and if the conjunction of the new moon fell out on the fourth day (= Wednesday), they fix the new moon on the fifth day (= Thursday); and if the conjunction of the new moon happened to fall on a Sabbath eve (= Friday), they fix the new moon on the seventh day (= Saturday)."
Footnotes:
[1] Mann (1920-1922) ii. 41-42 (document 13), erroneously identified as TS 8 J71 – "an error," according to Stern, "that has been carried over in most subsequent publications."
[2] Expressed in Hebrew by the mnemonics "BeDU," meaning, B=Monday; D=Wednesday; U (waw, 6th letter of Hebrew alphabet) = Friday.
[3] Expressed in Hebrew by the mnemonics "GeHaZ," meaning, G (gimel, 3rd letter of Hebrew alphabet) = Tuesday; H (he, 5th letter of Hebrew alphabet) = Thursday; Z (zayn), the 7th letter of Hebrew alphabet) = Saturday (Sabbath).
[4] Expressed in Hebrew by the mnemonics "ADU," meaning, A=Sunday; D=Wednesday; U (waw, the 6th letter of the Hebrew alphabet) = Friday.
[5] Stern (Calendar and Community, p. 282): "If the Day of Atonement and the Sabbath were contiguous, a person who died on the first of these days could not be buried till the third day, which is not acceptable."
[6] By a rabbinic ordinance, willow branches were to be taken up by Israel on the seventh day of Succoth (the Feast of Booths, or Tabernacles), in remembrance of the practice in the Temple precincts when the Temple still stood.
[7] The Hebrew word used here is havurah, which word is believed to be an idiom having the connotation of "a panel of judges," seeing that the intercalation of the month and year can only be done in a panel of three judges.
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Concerning the Exilarch's Letter, Sacha Stern explains in his book "Calendar and Community" (p. 184) that "Passover (15 Nisan) in that year was due to occur on a Tuesday; whilst according to the present-day rabbinic calendar, it should have occurred on Thursday."
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A Quick Note on the Subject of Intercalation of the Year (Leap Year)
As noted, there are 7 leap-years in a 19-year period. Their cycle is repeated in a regular order. For those that may be interested, Rabbi Dr. Sacha Stern wrote in his book, "Calendar and Community," p. 193:
"The intercalation is based on a fixed 19-year cycle, which starts year 1 (from the creation) and within which the following seven years are intercalated: 3, 6, 8, 11, 14, 17, 19..."
This is the cycle which repeats itself every 19 years.
© 2013 Created by Rav Mitterhoff.
