Ancient Calendar Systems Series
Hebrew Calendar
✦ ⁕ ✦
The Hebrew calendar is a lunisolar system that has run without a break for some 3,500 years, which means it follows both the Moon and the Sun. The religious year opens with Nisan in remembrance of the Exodus from Egypt, and the civil year opens with Tishrei in remembrance of Creation. In 358 CE the calendar moved from observation to calculation. Every month begins with the new crescent, every seventh day is given to rest, every seventh year to the rest of the land, and every fiftieth year to the release of debts and the return of property.
Why This Reconstruction?
The Hebrew calendar is the oldest calendar system of the ancient world still in everyday use. Mesopotamia's cuneiform tablets, Egypt's stone walls and the Greek parapegma now sit in museums. The Hebrew calendar, by contrast, still orders the daily life of a world Jewish population estimated at around 15 million people. Shabbat still begins on Friday evening, Pesach still falls on the 15th of Nisan, and Yom Kippur is still kept on the 10th of Tishrei. The dates of these days have been fixed by the same calculation for 1,600 years.
This calendar binds three separate layers of time into one system. In the lunar layer, each month opens with the new crescent and runs 29 or 30 days. In the solar layer, Pesach has to fall in spring every year. In the weekly layer, every seventh day is Shabbat. The Egyptian calendar followed the Sun alone, and the Islamic calendar follows the lunar month alone. Babylon tracked Moon and Sun together but had no weekly layer. The Hebrew calendar fits all three cycles together through a sevenfold arithmetic, and the result is the most intricate calendrical engineering the ancient world produced.
The matter is not arithmetic alone. The Hebrew calendar also carries a theology of sacred time. On the seventh day the person rests, and that day is Shabbat. In the seventh year the land rests, and that year is Shemitah. The fiftieth year, which follows seven Shemitah cycles, is the Yovel, and in that year slaves are freed and land returns to the families that first held it. The number seven therefore repeats at every scale, from the day to the month and from the year to the generation, and the mathematical rhythm of the cosmos is tied directly to social and economic justice. No other calendar system of the ancient world built so comprehensive a sacred-time ethic.
This tool opens that system up in order. For the Hebrew year you select it lists the twelve months, or thirteen in a leap year. For each month you can read its Babylonian-derived name, its older Canaanite or biblical name (Aviv, Ziv, Eitanim, Bul), its season, its agricultural work, and the festivals and significant days that fall in it. The Three Pilgrimage Festivals (Pesach, Shavuot and Sukkot) and the Yamim Noraim (Rosh Hashanah, Yom Kippur and the Days of Repentance between them) each have a section of their own. The Shemitah and Yovel cycles are explained in a further section. The heading on Hillel II's reform covers the move from observation to calculation in 358 CE and the Metonic arithmetic behind it. The Gezer Calendar, the oldest known Hebrew inscription and dated to the 10th century BCE, supplies the archaeological evidence for the link between farming and the calendar.
You will not find the grandeur of Babylon here, nor the monuments of Egypt, the philosophy of Greece or the law of Rome. What you find instead is an order of time that is still alive. It stops every seven days, returns to the land every seven years and resets ownership every fifty years. The Hebrew calendar is one of the few ancient systems that has reached us whole.
Year Selector
Here you can convert a Hebrew year (Anno Mundi, or AM) to its Gregorian equivalent and see where it sits in the 19-year Metonic cycle. Tishrei 1 and Nisan 1 are computed from the molad and the four dehiyyot, following the arithmetic that Hillel II fixed in 358 CE. In Jewish tradition AM 1 is the year of Creation, which corresponds to 3761 BCE.
Tishrei 1 = 23 September 2025 · Nisan 1 = 19 March 2026
The Dual New Year System
What sets the Hebrew calendar apart is that it holds two separate beginnings inside the same year. The Mishnah (ca. 200 CE) in fact recognises four new years, but two of them carry the main weight.
Religious New Year
Nisan 1
א בְּנִיסָן
Nisan opens the month in which the Exodus from Egypt took place. The Torah calls it "the first of the months of the year" (Shemot 12:2). The reigns of kings and the order of the pilgrimage festivals are both counted from Nisan. The older name of the month is Aviv, which means "spring", and Pesach is celebrated here.
Civil New Year
Tishrei 1
א בְּתִשְׁרֵי
Tishrei 1 is kept as the anniversary of Creation and carries the name Rosh Hashanah, "the head of the year". The AM year number advances on this date. Taxes, the Shemitah-Yovel count and the reckoning of the age of trees all begin from Tishrei. Tradition identifies the day with the creation of Adam. The name comes from the Akkadian tašrītu, meaning "beginning", and the month falls at the head of autumn, where the agricultural year turns over.
New Year for the Tithe of Animals
Elul 1
א בֶּאֱלוּל
According to the first, anonymous opinion in the Mishnah, the count of the tithe of livestock (ma'aser behema) begins on this date. Rabbi Elazar and Rabbi Shimon place it on Tishrei 1, and the halakha follows their view. In rabbinic tradition Elul is the month of repentance.
New Year of the Trees
Shevat 15
ט"ו בִּשְׁבָט
Tu BiShvat is the day on which the reckoning of the age of trees is renewed. That reckoning matters because the tithe (ma'aser) of fruit depends on it. The day was revived through the Kabbalistic seder tradition that grew up in 16th-century Safed, and in the modern era it has become a festival of tree-planting. It counts as a herald of spring, since almond trees in Israel begin to blossom around this time.
Shalosh Regalim · The Three Pilgrimage Festivals
The Torah commands three pilgrimage festivals (Shemot 23:14-17, Devarim 16:16). Three times a year all the men went up to Jerusalem "to appear before the Lord". Each of these festivals carries both the memory of a historical deliverance and a seasonal turning point in the harvest.
Pesach is the oldest and most central festival of the Hebrew calendar. The Book of Exodus commands it directly (Shemot 12), and it commemorates the deliverance of the Jewish people from slavery in Egypt. The historical dimension of the festival is preserved in the haggadah, the text read at the Seder table. The haggadah tells each generation to see itself as if it had gone out of Egypt on that very night ("bekhol dor vador hayyav adam lirot et atzmo ke'ilu hu yatza miMitsrayim").
At the agricultural root of the festival lies the beginning of the barley harvest. The phrase Hag haAviv ("Festival of New Growth") describes exactly that season. On 16 Nisan a measure of the new barley, the Omer, was offered at the Temple, and from that offering the 49-day count to Shavuot began. Because Pesach must fall in spring, the calendar is bound to a structural rule. The Metonic 19-year cycle and the added month of Adar I exist for that reason.
Food
Matzah (unleavened bread), maror (bitter herbs), karpas, charoset, egg, shank bone
Forbidden
Chametz (leavened grain products); the home is cleaned over ten days
Ritual
Seder (the night meal); reading of the Haggadah; four cups of wine; one cup for Elijah
In Synagogue
Shir haShirim (Song of Songs) is read
Shavuot falls fifty days after Pesach, on the day after the 49th day of the Omer. The name comes from that count, since shavuot means "weeks" and the reckoning runs 7x7 plus one. The agricultural dimension comes first. The wheat harvest begins here, and this was the day on which the first fruits (bikkurim) were brought to the Temple (Devarim 26:1-11). The farmer arrived with his basket and recited the formula that retells the story of deliverance.
The tradition that the Torah was given at Mount Sinai on this day took firm shape in the rabbinic period, around the 2nd and 3rd centuries CE. That development added a second theological layer to the festival, so that the harvest now stands beside the Torah and the first fruits beside the Revelation. Both layers are still observed today. The all-night study session known as Tikkun Leil Shavuot re-enacts the preparation for Mount Sinai.
Food
Dairy products (cheese, cheesecake); alluding to the saying "the Torah is milk and honey"
In Synagogue
The Book of Ruth is read; the Akdamut piyyut; Tikkun Leil Shavuot
Ritual
Symbolic offering of bikkurim; floral decoration (alluding to the connection between Torah and Sinai)
Astronomical
Falls at the beginning of summer; the same period as the heliacal (dawn) rising of the Pleiades (Hesiod also marks it as harvest-time)
Sukkot is the third of the Three Pilgrimage Festivals and the most joyful of them, since Devarim 16:14-15 commands "you shall rejoice in your festival". It arrives five days after Yom Kippur, so a festival of joy follows immediately on a day of purification. Its agricultural root is asif, the ingathering, when the grape, olive, date and fig harvest reaches its height. Its historical root is the memory of the people who lived in tents in the wilderness for forty years after the Exodus.
For seven days the household lives in the sukkah, a temporary booth. Its roof, the schach, has to be made of natural material, and the sky must remain visible through it. The arba minim or "four species" are waved during the festival: the lulav or palm branch, the etrog or citron, the hadas or myrtle, and the arava or willow. The waving turns towards God from the four directions and from heaven and earth. The eighth day brings Shemini Atzeret, which counts as a separate festival, and after it comes Simchat Torah, which marks the completion of the Torah-reading cycle. In Israel the two fall on the same day, and in the diaspora Simchat Torah follows a day later.
Ritual
Eating and (where possible) sleeping in the sukkah; waving the arba minim; the hoshana prayers
In Synagogue
Kohelet (Ecclesiastes) is read; hoshana each day, and on the final day Hoshana Rabba
Rain
The prayer for rain (geshem) is added on Shemini Atzeret; the threshold of the agricultural year
Mystical
Seven ushpizin (holy guests) are invited into the sukkah each night: Abraham, Isaac, Jacob, Moses, Aaron, Joseph, David
Yamim Noraim · The Days of Awe
The ten-day period between Rosh Hashanah and Yom Kippur is called Aseret Yemei Teshuvah, the "Ten Days of Repentance". It runs from 1 Tishrei to 10 Tishrei and forms the most intense stretch of the Jewish liturgical year, built on the themes of judgment, repentance and atonement.
Tishrei 1-2
Rosh Hashanah
Yom haDin · Day of Judgment. The shofar is sounded 100 times. God writes each person into one of three books: the book of the righteous, the book of the wicked, and the book of those in between.
Tishrei 3-9
Days of Repentance
Aseret Yemei Teshuvah. For seven days the community recites selichot (penitential prayers), repairs broken relationships (tikkun) and gives tzedakah (charity). The fast of Tzom Gedaliah falls on the third day.
Tishrei 10
Yom Kippur
Yom haKippurim · Day of Atonement. The fast runs 25 hours, and the synagogue holds five prayer services, opening with Kol Nidre and closing with Ne'ilah. The three books are sealed on this day.
Rosh Hashanah is one of the four new years the Mishnah defines, and it is the point at which the AM year number advances. The day is kept as the anniversary of Creation, in the words "hayom harat olam", "today the world was conceived". As the Day of Judgment it holds that God judges all humanity, but the verdict is not sealed at once, and ten days of repentance remain open until Yom Kippur.
The central ritual is the shofar, the ram's horn, sounded a hundred times in all through the sequences called tekiah, shevarim and teruah. Tradition reads three meanings into the sound: a summons to judgment, a remembrance of Mount Sinai and a call towards the messianic age. In the Tashlich ritual the worshipper goes to flowing water and symbolically casts away his sins. The table carries its own symbols. Apple with honey asks for a sweet year, pomegranate asks for merits as numerous as the 613 mitzvot, and the head of a fish asks that the coming year find one at the head rather than the tail.
Shofar
100 blasts; sequences of tekiah-shevarim-teruah; rabbinic mitzvot
Food
Apple with honey, pomegranate, fish head; seven symbolic foods of the simanim
Prayer
In Musaf: the three sections of Malkhuyot, Zikhronot, and Shofarot; Avinu Malkenu
Greeting
Shanah tovah ("A good year"); L'shanah tovah tikatevu ("May you be inscribed for a good year")
Yom Kippur is the holiest day of the Jewish calendar. The Torah commands "you shall afflict your souls" (Vayikra 16:29-31, 23:27-32), and the rabbinic tradition reads that command through five classical prohibitions: eating and drinking, bathing, anointing with oil, leather shoes and marital relations. The fast runs a full 25 hours, from the appearance of the stars one evening to the stars of the next.
The synagogue holds five prayer services on this day: Maariv (Kol Nidre), Shacharit, Musaf, Mincha and Ne'ilah. The Kol Nidre evening prayer annuls vows, and historically it annulled before God those vows that had been extorted under coercion, above all in the Marrano period. The closing service, Ne'ilah, is the climax of the day and stands as the last chance before the gates of heaven shut. The congregation recites the Vidui, the confession of sins, together. Its alphabetical ordering and impersonal form give the confession a collective rather than an individual voice.
Yom Kippur and Tisha b'Av are the only two full-day fasts of the Jewish calendar, and their meanings run in opposite directions. Tisha b'Av is a fast of catastrophe and mourning, while Yom Kippur is a fast of purification and hope. That opposition sits at the centre of the calendar's theological architecture.
Prohibitions
Eating and drinking, bathing, anointing with oil, wearing leather shoes, marital relations
Five Services
Kol Nidre · Shacharit · Musaf · Mincha · Ne'ilah
Attire
A white kittel (resembling burial shrouds); a symbolic purification
Closing
The final shofar blast (long tekiah); "Le'shanah haba'ah biRushalayim!"
Shabbat · The Seventh Day
Shabbat is the heartbeat of the Hebrew calendar. Every seventh day it brings a 25-hour pause that runs from the appearance of the evening stars to the same hour on the following evening. It reflects the seventh day of the Creation account, and the whole structure of the calendar rests on that rhythm.
שַׁבָּת
"Shabat" · To cease, to stop, to rest
SHABBAT
Shabbat is the only unit of the calendar with no astronomical referent. It depends on neither the Moon, nor the Sun, nor the stars, and takes its rhythm solely from the Creation account. According to Bereshit 2:2-3, on the seventh day God "finished His work and rested". In the theology of the Hebrew calendar that sentence explains why the week runs to seven days, since seven is the number of rest.
The weekly cycle was unknown in the ancient Near East. Babylon divided its 30-day months into three ten-day segments, and the Egyptian decans ran ten days as well. The seven-day week is an Israelite invention, and it spread from there into the Greco-Roman world and later into the modern one. The seven planets of Babylon, that is the Sun, the Moon and the five classical planets, may lie behind the number. Even so, the Torah frames the day in ethical and theological terms rather than astronomical ones, because the seventh day belongs to rest and not to a moon-god or a stellar calculation.
The halakhic tradition lists 39 principal categories of forbidden work, the melachot, in Mishnah Shabbat 7:2. These categories are drawn from the labours performed in building the Tabernacle (Mishkan). The shared principle is that one does no creative work and does not interfere with the natural order. In modern practice this means kindling no fire, which includes electricity, and refraining from writing, from trade, from riding animals and from financial transactions.
The sociological force of Shabbat is considerable. For 3,500 years a people that stops every seventh day has held on to its own calendrical identity against the pressure of production, the demands of rulers and the conditions of war. Abraham Joshua Heschel describes Shabbat as "a palace in time", and on his reading this sacred precinct is built not in space but in time.
Kindling fire
Writing
Commerce
Counting money
Cooking
Sewing
Harvesting
Carrying loads
Crossing thresholds
Weighing
Tuning
Using electricity
Shabbat is also family time. On Friday evening the household welcomes the day with kabbalat Shabbat, kindles the candles, says kiddush over wine and blesses the braided challah bread. Three family meals are eaten across the day. Intimate time between spouses is commanded as oneg Shabbat, the delight of Shabbat. The third meal, se'udat shlishit, is taken on Saturday afternoon. In the evening the havdalah ritual closes the day with a blessing over wine, spices and a braided candle, and the household returns to the world of the weekday.
Shemitah and Yovel · The Rest of the Land and of Society
The weekly rhythm of Shabbat widens at the scale of the year into Shemitah, the seventh year. At the scale of a generation it reaches Yovel, the fiftieth year that follows seven Shemitah cycles. Together they form the most comprehensive sacred-time ethic of the ancient world, one that resets the land, the economy and the social order at fixed intervals.
Shemitah · The Seventh Year
Sabbath of the Land · Remission of Debts · "The Year of Release"
שְׁמִטָּה
Vayikra 25:1-7 and Devarim 15 command a seven-year cycle. In every seventh year the land keeps a Shabbat, which means that sowing, harvesting and pruning are all forbidden. Whatever grows on its own counts as ownerless and is open to everyone, so the poor and the stranger may gather from it freely. The word Shemitah means "release", and it describes the release of the land, of the produce and of ownership itself.
Devarim 15:1-3 adds a further rule to Shemitah, the remission of debts. Debts owed by one Jew to another are cancelled automatically at the end of the Shemitah year. The rule limits how far debt can accumulate and keeps the poor from carrying debt from one generation into the next. Hillel the Elder, in the 1st century BCE, developed a legal mechanism called prozbul to make the rule workable in practice. Under prozbul the creditor assigns the debt to the court, and the debt is then exempt from Shemitah remission.
Shemitah is still kept in Israel today, most recently in the year 5782, which fell in 2021-2022. Two main solutions are open to the modern Israeli farmer. The first is heter mechira, under which the land is sold symbolically to a non-Jew for the Shemitah year, though Orthodox circles dispute this route. The second is otzar beit din, under which cultivation passes to the supervision of a rabbinical court. In both cases the religious care owed to the produce (kedushat shevi'it) is preserved.
In the seventh year the land rests, debts are remitted and ownership is suspended for a time.
Yovel · The Fiftieth Year
After Seven Shemitot · The Jubilee · The Great Reset
יוֹבֵל
Vayikra 25:8-13 commands that once seven Shemitah cycles are complete, that is after 49 years, the fiftieth year becomes the Yovel. The word Yovel in fact means "ram's horn", and it carries the same sense in Joshua 6:4-5. The name comes from the practice of proclaiming the Yovel year with the shofar on the morning of Yom Kippur. The words of the proclamation are "Proclaim liberty throughout all the land" (Vayikra 25:10), and the same verse is inscribed on the Liberty Bell in the United States.
The Yovel year has three principal effects. First, the land rests, as it does in Shemitah, so that neither the 49th nor the 50th year is sown. Second, slaves are freed, and Hebrew slaves sold fifty years earlier regain their freedom and return to their families. Third, the land is returned, and agricultural land sold fifty years earlier reverts to the family that first held it. This mechanism resets economic inequality structurally and keeps land from collecting in a few hands across the generations.
The sociological radicalism of Yovel is striking. Under this system private property is never absolute. Every family holds ancestral land granted by God, and a sale works like a temporary lease capped at fifty years. Vayikra 25:23 states the principle plainly: "The land shall not be sold in perpetuity, for the land is mine." Modern law knows no comparable theory of property.
Historically, after the Babylonian exile of 586 BCE, Yovel was no longer kept in practice. The Talmudic debates concluded that it applies only when all twelve tribes dwell in the Land of Israel (Arakhin 32b). The State of Israel does not observe Yovel today either, and keeps only Shemitah. Yovel survives not as a rule in force but as an ethical model that is still argued over.
The Metonic 19-Year Cycle
The Metonic cycle is the mathematical heart of the Hebrew calendar. Nineteen solar years come to roughly 235 lunar months. This equivalence was discovered in the ancient Near East, and it keeps the Moon and the Sun in balance. The cycle was taken over during the Babylonian exile and fixed by Hillel II's reform in 358 CE.
The basic problem of a lunisolar calendar is this: twelve lunar months run about 354 days, while the solar year runs 365.25 days. The gap of roughly eleven days accumulates from year to year. Over a decade it reaches 110 days, and within a single generation the seasons would turn upside down. Since Pesach has to fall in spring, the calendar needs an extra month inserted at regular intervals.
In the early 5th century BCE Babylonian mathematicians found the equivalence 19 solar years ~ 235 lunar months. When seven intercalary months are added across a 19-year cycle, so that seven of the nineteen years run to thirteen months, the Moon and the Sun agree on average. The Greek astronomer Meton introduced the cycle in Athens in 432 BCE, and the Greeks named it after him. Parker and Dubberstein show in Babylonian Chronology 626 B.C.-A.D. 75 that the Babylonians had known it considerably earlier, by the beginning of the 5th century BCE.
Hillel II's reform of 358 CE embedded this Metonic cycle formally in the Hebrew calendar. The leap years are years 3, 6, 8, 11, 14, 17 and 19 of the 19-year cycle. In those years a 30-day Adar I is inserted before Adar. Pesach still falls on 15 Nisan, but because Nisan itself shifts back by a few weeks, the festival lands in spring.
Regular year (12 months)
Leap year (13 months)
A 19-year cycle holds 12 regular years and 7 leap years. The total comes to 12 x 12 + 7 x 13 = 235 months. Multiplying out gives 235 x 29.5306 = 6,939.7 days, against 19 x 365.2422 = 6,939.6 days. The difference amounts to only about 2 hours across 19 years, and a drift of one full day accumulates over roughly 220 years.
Hillel II's Reform · From Observation to Calculation
In 358-359 CE the Patriarch Hillel II moved the Hebrew calendar from a system based on observation to one based on calculation. This is the most important calendar reform in Jewish history, and it laid the foundation for 1,600 years of unbroken operation.
The Pre-Reform System (6th c. BCE - 358 CE)
During the Second Temple and Talmudic periods the Hebrew calendar rested on two principal mechanisms. The first was Rosh Chodesh, the start of a new month, which was settled by witnesses. Two trustworthy Jews reported to the Sanhedrin, the Jewish High Court, that they had seen the new crescent, the court confirmed the sighting, and the month officially began. The second was ibbur, the insertion of a leap month, which depended on agricultural observation. If spring came late, if the barley had not ripened, or if the lambs had not yet been born, the court added a second Adar, Adar Sheni, after Adar.
Under this system the decision came out of Jerusalem every month. The Sanhedrin's rulings reached the Babylonian and Persian diaspora through beacon signals and messengers. The Roman Empire then crushed Jewish autonomy over the 2nd to 4th centuries CE, and Constantius II (337-361) forbade the Sanhedrin to convene or to proclaim new months. As a result, festivals began to be kept on different days across a diaspora that spanned continents.
Hillel II's Solution (358-359 CE)
Patriarch Hillel II, as head of the Sanhedrin, decided to make the "hidden science" of calendar calculation public. From then on the calendar would depend on mathematics rather than on witnesses. The reform rested on three principal decisions.
Before (Observational)
Rosh Chodesh by Witnesses
The Sanhedrin determined the new month from witness testimony, and the ruling was carried outward by beacon and messenger.
The leap month (ibbur) depended on agricultural observation, and the criteria were the ripening of the barley and the birth of the lambs.
After (Calculated)
By the Molad Calculation
The new month is calculated from the molad, the mean conjunction. The interval between two moladot is 29 days, 12 hours and 793 chalakim (1 chalak = 1/1080 of an hour).
Leap years are fixed at years 3, 6, 8, 11, 14, 17, and 19 of the 19-year Metonic cycle.
The molad constant of 29 days, 12 hours and 793 chalakim, which comes to about 29.530594 days, is remarkably accurate. It differs from the true mean synodic month of 29.530588 days by a matter of seconds. That precision most likely goes back to the lunar eclipse records of the 8th to 5th centuries BCE, on which the Babylonian System B calculations of around 300 BCE were based. Hipparchus and Ptolemy used the same value (Almagest, 2nd c. CE).
The reform was not completed in a single stroke. Hai Gaon, writing in the 10th century, holds that only the formalisation of the 19-year cycle can be credited to Hillel himself. The remaining details, such as the lengths of the months and the postponement rules known as dehiyot, developed over the following centuries. Sacha Stern's work shows that the fixed calendar reached its final form only in 922-924 CE. The underlying structure is still attributed to Hillel II.
What the reform really changed was where authority lay. The Jewish calendar no longer depended on the immediate decision of a political authority, that is the Sanhedrin, but on a mathematical formula. Every Jewish community in the diaspora could now work out its own calendar without waiting for a ruling from Jerusalem. The calendar thereby became independent of imperial pressure.
The Gezer Calendar · The Oldest Hebrew Inscription
The Gezer Calendar dates to the 10th century BCE, the Solomonic era. It is a limestone tablet of about 11 x 7 cm, and it counts as the oldest known Hebrew, or paleo-Canaanite, inscription. The text is an agricultural calendar, and it supplies the archaeological evidence for Jewish calendar knowledge.
The Tablet and Its Discovery
R.A.S. Macalister, 1908 · Today held at the Istanbul Archaeology Museum
The Irish archaeologist R.A.S. Macalister found the tablet in 1908, during excavations at Gezer some 30 km west of Jerusalem. It stands 11.1 cm tall and 7.3 cm wide, roughly the size of a mobile phone. It is written in the paleo-Hebrew, or Early Canaanite, alphabet, and in the lower corner appears what is probably the name of the scribe, "Abiya". Palaeographic analysis dates it to the 10th century BCE, so it may have been written somewhere between the reign of King Solomon and the campaign of the Egyptian pharaoh Shishak.
Because the excavation took place on Ottoman territory, the tablet is exhibited today at the Istanbul Archaeology Museums. A replica is also held at the Israel Museum. The text runs through the twelve months of the agricultural year, but instead of naming the months it names the work done in each one.
The Text (Seven Lines)
𐤉𐤓𐤇𐤅 𐤀𐤎𐤐
"Two months of ingathering" (Tishrei-Cheshvan; olives, dates, figs)
𐤉𐤓𐤇𐤅 𐤆𐤓𐤏
"Two months of sowing" (Kislev-Tevet; wheat, barley)
𐤉𐤓𐤇𐤅 𐤋𐤒𐤔
"Two months of late sowing" (Shevat-Adar; legumes, vegetables)
𐤉𐤓𐤇 𐤏𐤑𐤃 𐤐𐤔𐤕
"One month of flax harvest" (Nisan; flax is uprooted with its roots)
𐤉𐤓𐤇 𐤒𐤑𐤓 𐤔𐤏𐤓𐤌
"One month of barley harvest" (Iyar; the Omer period from Pesach to Shavuot)
𐤉𐤓𐤇 𐤒𐤑𐤓 𐤅𐤊𐤋
"One month of wheat harvest and measuring" (Sivan; the agricultural root of Shavuot)
𐤉𐤓𐤇𐤅 𐤆𐤌𐤓
"Two months of vine pruning" (Tammuz-Av)
𐤉𐤓𐤇 𐤒𐤑 𐤀𐤁𐤉
"One month of summer fruit" (Elul; the season when figs and dates are dried and gathered)
The key word is yerah (𐤉𐤓𐤇), which means "month" and covers both the Moon in the sky and the month of the calendar. The form yerahw carries the dual ending and means "two months". The inscription gives a complete breakdown of the twelve-month agricultural year, beginning at Tishrei and running through to Elul.
This inscription documents three things. First, the Israelites and Canaanites living at Gezer in the 10th century BCE already used a twelve-month calendar system. That is 400 years before the Babylonian exile, so the system was in place while the Babylonian month names were still unknown. Second, the cycle of agricultural work forms the concrete ground of the Jewish festivals. Pesach falls in Aviv because the barley harvest falls in that month, Shavuot comes fifty days later because the wheat harvest falls in that season, and Sukkot falls in Tishrei because the ingathering peaks then. The festivals sit directly on top of the farming year. Third, the tablet is one of the earliest known Hebrew inscriptions, and it attests to the continuity of Jewish writing and calendar knowledge.
The Architecture of Sacred Time
The theological core of the Hebrew calendar lies in the way it turns a mathematical structure of time into an ethical order. This is the most comprehensive system of sacred time the ancient world is known to have produced.
The Structural Repetition of Seven
The Hebrew calendar builds itself on the cyclical repetition of seven. Seven days make a week, and the last of them is Shabbat. Seven weeks make the Omer count, which runs 7x7, or 49 days, from Pesach to Shavuot, with Shavuot itself on the fiftieth day. Seven months carry the passage from the religious year to the civil one, since seven months separate Nisan from Tishrei. Seven years complete the Shemitah cycle. Seven times seven years reach the Yovel, where the fiftieth year after 49 resets everything.
What emerges is a fractal cosmological architecture. The same sevenfold pattern repeats in the day, the week, the month, the year and the generation. The microcosm of the week is mirrored in the macrocosm of the generation, and one law operates across every time-scale. The structure differs from the Hindu Vedic yugas, because those count out cosmic durations while this repetition sets up an ethical rhythm. Here the number seven stands for sanctity rather than for nature.
Memory and Anticipation
The Hebrew calendar has two faces, a memory that looks back and an expectation that looks forward. Pesach recalls the Exodus from Egypt, Shavuot recalls the receiving of the Torah at Sinai, and Sukkot recalls the forty years spent in tents in the wilderness. Those festivals look back. Rosh Hashanah renews the judgment each year, Yom Kippur renews the pardon each year, Shemitah restarts the economy every seven years, and Yovel resets ownership every fifty. Those look forward. The calendar therefore works as an archive and a programme at the same time.
Messianic expectation is added on top of this double structure. At the close of every Yom Kippur the congregation says "Le'shanah haba'ah biRushalayim", "Next year in Jerusalem", and the same words end every Pesach Seder. Each festival therefore opens onto a deliverance that has not yet happened. No other calendar of the ancient world carries so explicit an orientation towards the future.
The Moving Marketplace, the Steady Palace
The experience of the Jewish diaspora changed the character of the calendar. Communities in exile lived cut off from land, from kingdom and from Temple, and the one structure left to them in common was time. Abraham Joshua Heschel describes the result as an "architecture of time", in which a people unable to build palaces in space built them in time instead. Every Shabbat is a palace, every festival a vaulted gateway and every Shemitah a courtyard. The calendar became the principal carrier of Jewish identity.
This structure is the form in which Judaism took in the cosmology of the ancient Near East and gave it an ethical shape. The calendrical knowledge of Egypt, Babylon and Mesopotamia was received, and the Babylonian month names, the Metonic cycle and the synodic-month constant all came with it. That knowledge was then taken out of the hands of political authority and made the shared mathematical property of the community. Hillel II's reform is the last stage of that transition, since the calendar now rests on a formula anyone can apply rather than on an emperor's decree.
Primary and Secondary Sources
The classical, academic and technical sources on which this reconstruction relies are listed below. The list begins with the Torah and the Talmud and runs through to modern mathematical scholarship.
- Tanakh (the Hebrew Bible): Shemot 12, 23, 34 (festivals); Vayikra 23, 25 (Shemitah-Yovel); Devarim 16; Bemidbar 9 (Pesach Sheni).
- Mishnah (ca. 200 CE): tractates Rosh haShanah (new years, calendar reckoning), Shabbat (the 39 melachot), Shevi'it (the rules of Shemitah).
- Talmud Bavli: Rosh haShanah 8a-25b (debates on new years and the mathematics of intercalation); Sanhedrin 11a-b (decisions on leap years); Arakhin 32b (the historical application of Yovel).
- Bnei Yissachar, Rabbi Tzvi Elimelech Spira (1850), Kabbalistic analyses of the monthly lessons.
- Maimonides, Mishneh Torah, Hilchot Kiddush HaChodesh (Laws of the Sanctification of the New Moon), mid-12th c.; the systematic exposition of calendar mathematics.
- al-Biruni, al-Athar al-Baqiyah (ca. 1000 CE), Chapter 7 (the Jewish calendar); trans. C. E. Sachau, The Chronology of Ancient Nations, London, 1879.
- Eduard Mahler, Handbuch der jüdischen Chronologie, Leipzig: Fock, 1916. A classical reference.
- Sacha Stern, Calendar and Community: A History of the Jewish Calendar 2nd Century BCE - 10th Century CE, Oxford: Oxford University Press, 2001. The modern academic standard.
- Sacha Stern, Calendars in Antiquity: Empires, States, and Societies, Oxford, 2012.
- Bonnie Blackburn and Leofranc Holford-Strevens, The Oxford Companion to the Year, Oxford, 1999. A comprehensive calendrical atlas.
- Arthur Spier, The Comprehensive Hebrew Calendar, Jerusalem: Feldheim, 1986. Practical conversion tables.
- Nathan Bushwick, Understanding the Jewish Calendar, New York: Moznaim, 1989. A pedagogical introduction.
- David M. Russinoff, "Understanding the Hebrew Calendar," russinoff.com/calendar/calendar.pdf, 2014. A mathematical analysis.
- Edgar Frank, Talmudic and Rabbinical Chronology, New York: Feldheim, 1956.
- Solomon Gandz, "The Calendar of Ancient Israel," in Homenaje a Millas-Vallicrosa, vol. 1, Barcelona, 1954: 623-646.
- Parker and Dubberstein, Babylonian Chronology 626 B.C. - A.D. 75, Providence: Brown University Press, 1956. On the Babylonian origins of the Metonic cycle.
- Otto Neugebauer, A History of Ancient Mathematical Astronomy, Berlin: Springer, 1975. A classical reference.
- R.A.S. Macalister, "Excavation of Gezer" (3 vols.), London: Murray, 1912. The original publication of the Gezer tablet.
- W. F. Albright, "The Gezer Calendar," BASOR 92 (1943): 16-26. A classical philological analysis.
- Shmuel Aḥituv, Echoes from the Past: Hebrew and Cognate Inscriptions from the Biblical Period, Jerusalem: Carta, 2008.
- Abraham Joshua Heschel, The Sabbath: Its Meaning for Modern Man, New York: Farrar, Straus and Giroux, 1951. A philosophical-theological analysis of Shabbat.
- Moshe Idel, Kabbalah: New Perspectives, New Haven: Yale University Press, 1988 (especially on the Tu BiShvat seder).
- Adin Steinsaltz, The Essential Talmud, New York: Basic Books, 1976; an introductory presentation of tractate Rosh haShanah.
- Jeffrey L. Rubenstein, The History of Sukkot in the Second Temple and Rabbinic Periods, Atlanta: Scholars Press, 1995.
- Hayyim Schauss, The Jewish Festivals: A Guide to Their History and Observance, New York: Schocken, 1938.
FULL LIST
Hebrew Month and Festival Index
Below are the thirteen months of the Hebrew calendar, with Adar II appearing in leap years only. Each entry gives the Hebrew spelling, the transliteration, the pre-exilic name and the festivals of the month. The calculator above follows the reckoning fixed by Hillel II.
Nisan (נִיסָן) Nīsān
formerly Aviv, Spring; the season when the barley ripens · Akkadian Nisannu ("beginning"); traceable to the Sumerian root nisag ("first fruits") · March-April · 30 days · Early spring (March-April) · Nisan is the month of the Exodus from Egypt, and the Torah calls it "the head of the months" (Shemot 12:2). Its old Canaanite name is Aviv, the season when the barley ripens, and the phrase Hag ha-Aviv ("Festival of Spring") is used for Pesach. After the Babylonian exile the Akkadian name Nisannu took hold. No ta'anit (fast) is held in this month and no tachanun (penitential prayer) is recited, so the whole month carries a half-festive character. Pesach runs from 14 to 21 Nisan as a seven-day pilgrimage festival, or eight days outside Israel.
- Rosh Chodesh Nisan
- Beginning of the religious year; the Tabernacle (Mishkan) was dedicated on this date (Shemot 40)
- Eve of Pesach
- Korban Pesach; the shift to matzah; the final stage of cleaning the house
- Pesach (Shalosh Regalim)
- The Exodus from Egypt; abstention from work on the first and last days; the seder on the first two evenings
- Beginning of the Omer Count
- The 49-day count to Shavuot begins
- Yom HaShoah
- Holocaust and Heroism Remembrance Day (modern, 1959)
Iyar (אִיָּר) ʾIyyār
formerly Ziv, Brightness, radiance; the season when flowers bloom · Akkadian Ayyaru ("rosette, flower"); Sumerian guḫ-ḫul · April-May · 29 days · Spring (April-May) · Its older Canaanite name is Ziv, and 1 Kings 6:1 names it as the month in which Solomon began building the Temple. Iyar follows Pesach and falls inside the counting of the Omer. Tradition keeps it as a season of partial mourning in memory of the death of Rabbi Akiva's disciples, and weddings are not held. On the 33rd day, Lag baOmer, the mourning is lifted and celebration is allowed. In the Shephelah and the Galilee the crops begin to ripen during this month.
- Yom HaAtzmaut
- Israeli Independence Day (modern, 1948; 5 Iyar = 14 May 1948)
- Pesach Sheni
- Second Pesach; the Torah's provision for those who missed the first (Bemidbar 9)
- Lag baOmer
- The 33rd day of the Omer; the yahrzeit of Rabbi Shimon bar Yochai; bonfires are lit and weddings held
- Yom Yerushalayim
- The reunification of Jerusalem (modern, 1967)
Sivan (סִיוָן) Sīwān
Akkadian Simānu ("time, season") · May-June · 30 days · Late spring to early summer (May-June) · Tradition holds that the Torah was given at Mount Sinai in this month, and Shavuot falls here. The wheat harvest begins, and the phrase Hag haKatzir ("Festival of the Harvest") is used for Shavuot. The Omer count reaches its end here, since Shavuot arrives once the 49th day is complete. Sivan 6-7, kept as one festival day in Israel and two outside it, forms one of the most important intervals of the year. The Book of Esther records that the king's decrees were issued in this month.
- Shavuot (Shalosh Regalim)
- The Giving of the Torah; the Revelation at Sinai; Tikkun Leil Shavuot (all-night Torah study); dairy foods are eaten
Tammuz (תַּמּוּז) Tammūz
Sumero-Akkadian Dumuzi/Tammūzu; a fertility god, the young god whose descent into the underworld is mythologised · June-July · 29 days · Early summer (June-July) · The name comes from the pagan god Tammuz, the Sumerian Dumuzi, and was taken over during the Babylonian exile. Jewish tradition knew the origin of the name and kept it all the same. A period of mourning opens in this month. On 17 Tammuz the Babylonian and Roman sieges breached the walls of Jerusalem, and the date is kept as a fast. The Three Weeks (bein hametzarim, "between the straits") follow and run until Tisha b'Av, and during them weddings, music and haircuts are forbidden.
- Shiva Asar b'Tammuz (Fast)
- The breaching of the walls of Jerusalem in the Babylonian and Roman sieges
- Beginning of the Three Weeks
- The mourning period leading up to Tisha b'Av; bein hametzarim
Av (אָב) ʾĀv
Akkadian Abu; in Jewish tradition the meaning "father" is emphasised · July-August · 30 days · Summer (July-August) · Av is the most mournful month of the Jewish calendar. Mourning reaches its peak over the first nine days, when neither meat nor wine is consumed. Both the First and the Second Temple were destroyed on the 9th of Av, in 586 BCE and 70 CE, and tradition attributes further catastrophes to the same day, among them the crushing of the Bar Kokhba revolt, the expulsion of the Spanish Jews in 1492 and the outbreak of the First World War. Tisha b'Av is a full-day fast of 25 hours, with abstention from water, bathing, leather shoes and marital relations, and Eichah (Lamentations) is read. The 15th of the month, Tu b'Av, then brings the most joyful day, on which young women danced in the fields and prospective spouses were matched (Talmud Ta'anit 26b).
- Tisha b'Av (Fast)
- The destruction of both Temples; the deepest day of mourning in Jewish history
- Tu b'Av
- Day of joy; said in tradition to be the happiest day in Jewish history
Elul (אֱלוּל) ʾĔlūl
Akkadian Ulūlu; probably meaning "harvest, gathering." In Jewish mysticism, the initials of the verse from Song of Songs 6:3: E-L-U-L · August-September · 29 days · Late summer (August-September) · Elul is the month of preparation for the High Holy Days. From the first of the month the shofar, the ram's horn, is sounded every morning, and the worshipper readies himself for Rosh Hashanah and Yom Kippur. Selichot, the penitential prayers, also begin in this month. Jewish mysticism describes Elul as the month in which "the King is in the field", meaning that God leaves the palace and comes close to the people. The harvest ends here, and according to the first opinion in the Mishnah the tithe of livestock (ma'aser behema) is reckoned from this month.
- Rosh Chodesh Elul
- Beginning of the month of repentance; the shofar begins to be sounded in the mornings
- Intensification of Selichot
- In the days near Rosh Hashanah, nightly prayers intensify (Ashkenazi custom)
Tishrei (תִּשְׁרֵי) Tišrey
formerly Eitanim, The month of perennial streams (waters that flow continually); the enduring, the strong · Akkadian tašrītu ("beginning") · September-October · 30 days · Early autumn (September-October) · Tishrei is the most crowded month of the Jewish calendar, since the civil new year (Rosh Hashanah), Yom Kippur, Sukkot, Shemini Atzeret and Simchat Torah all fall within it. Its older Canaanite name is Eitanim (1 Kings 8:2), and Solomon is recorded to have dedicated the Temple in this month. A span of 22 days carries the most theologically dense period of the Jewish year, moving from judgment on days 1 to 10, to purification on the 10th, to rejoicing and the remembrance of the booth from the 15th to the 21st, and to closure on the 22nd. After Sukkot the geshem prayer, the prayer for rain, is added to the liturgy.
- Rosh Hashanah
- The civil new year; the anniversary of Creation; Yom haDin (Day of Judgment); the shofar is sounded 100 times
- Days of Repentance (Aseret Yemei Teshuvah)
- The ten days between Rosh Hashanah and Yom Kippur
- Tzom Gedaliah (Fast)
- The assassination of Gedaliah ben Achikam (586 BCE)
- Yom Kippur
- Day of Atonement; the holiest day of the year; 25 hours of fasting and prayer
- Sukkot (Shalosh Regalim)
- Festival of Booths; commemoration of forty years in tents in the wilderness; meals are taken in the sukkah, the arba minim are waved
- Shemini Atzeret
- The eighth day of Sukkot; a separate festival; the prayer for rain begins on this day
- Simchat Torah
- The completion and restart of the Torah-reading cycle; joyful dancing
Cheshvan (מַרְחֶשְׁוָן) Marḥešvān
formerly Bul, Produce, yield; rain (after the Akkadian root) · Akkadian Araḥsamna ("eighth month"); the prefix "Mar" is also taken to mean "bitter," since Cheshvan contains no festivals · October-November · 29 days · Autumn (October-November) · Cheshvan is the only month that holds no festival apart from Shabbat, and for that reason tradition calls it Mar-Cheshvan, "Bitter Cheshvan". Its older name is Bul (1 Kings 6:38), and Solomon completed the Temple in this month, though the dedication was postponed to Tishrei. The rainy season begins here, and in Israel the geshem prayer is added to the daily amidah from the 7th of the month. A messianic tradition holds that the future Temple will be dedicated in Cheshvan, which would settle the month's "festival debt".
- Beginning of the Geshem Prayer
- In Israel, the prayer for rain is added to the amidah (in the diaspora, from the 60th day after the autumnal equinox)
Kislev (כִּסְלֵו) Kislew
Akkadian Kislīmu; probably meaning "hope" (kesel = loins) or "the seeping of hope" · November-December · 29 days · Late autumn to winter (November-December) · Kislev is the month of Hanukkah. It covers the darkest part of the year, and the festival of light is kept as the tekufat Tevet, the winter solstice, draws near. Hanukkah begins on 25 Kislev and lasts eight days, running from Kislev 25 to Tevet 2 or 3 depending on the length of the month. It commemorates the Maccabees' victory over Hellenistic oppression and the rededication of the Temple in 164 BCE. The menorah is kindled with one additional candle each night, and it is displayed at the door or in the window.
- Beginning of Hanukkah
- Festival of Lights; eight days; the rededication of the Temple (164 BCE)
Tevet (טֵבֵת) Ṭēvēt
Akkadian Ṭebētu ("the month of rains arriving") · December-January · 29 days · Winter (December-January) · The last days of Hanukkah fall on Tevet 2-3. The fast of the 10th of Tevet follows, marking the day on which Nebuchadnezzar began the siege of Jerusalem in 588 BCE, which tradition counts as the start of the destruction of the First Temple. In Israel the same day serves both as a fast and as the day of Kaddish Klali for Holocaust victims. The cold, rainy season peaks here, as the early rains (yore) end and the steady rainy period (malkosh) sets in.
- End of Hanukkah
- The final days of the eight-day festival
- Asarah b'Tevet (Fast)
- The beginning of Nebuchadnezzar's siege of Jerusalem; in the modern era, the day of Kaddish Klali
Shevat (שְׁבָט) Šəvāṭ
Akkadian Šabāṭu ("to strike, to lash"; probably an allusion to violent rainstorms) · January-February · 30 days · Late winter (January-February) · Shevat holds the new year of the trees. On 15 Shevat, Tu BiShvat, the age of every tree advances by one year, and that reckoning governs the tithe of fruit. The almond trees in Israel begin to blossom around this date, which is the first physical sign that spring is on the way. The Lurianic Kabbalists of 16th-century Safed developed the Tu BiShvat seder, a ritual meal of four cups of wine and thirty different fruits that corresponds to the four Kabbalistic worlds. In modern Israel the day is kept as a day of tree-planting.
- Tu BiShvat
- New Year of the Trees; Kabbalistic seder; modern day of tree-planting
Adar (אֲדָר) ʾĂdār
Akkadian Addaru; probably meaning "grain, threshing time" · February-March · 29 days · Late winter to early spring (February-March) · Adar is the month of joy, as the Talmud puts it: "Mishe nichnas Adar marbim besimcha" ("When Adar enters, joy increases", Talmud Ta'anit 29a). Purim is celebrated on 14 Adar in memory of the deliverance recorded in the Book of Esther. In a leap year of thirteen months a 30-day Adar I is inserted and the festivals move to the regular Adar, which is called Adar II in such years, because Megillat Esther requires Purim to fall close to Pesach. Adar I holds no festivals of its own, yet its days are still kept with joy.
- Ta'anit Esther (Fast)
- Commemorating the fast that Esther observed for her people
- Purim
- The deliverance of the people through Esther and Mordechai in the Persian Empire; the Megillat Esther is read, costumes are worn, festive meals are held
- Shushan Purim
- In ancient walled cities (Jerusalem), Purim is celebrated the day after
Adar I (אֲדָר א') ʾĂdār ʾĀlef
The thirteenth month added in a leap year; also known as "Veadar" ("and Adar") · Around February · 30 days · Late winter (February) · Adar I is inserted in years 3, 6, 8, 11, 14, 17 and 19 of the 19-year Metonic cycle. It corrects the drift between the season and the lunar month and keeps Pesach in spring. In this way the arithmetic carries out the Torah's commandment of "Hag ha-Aviv" (Shemot 23:15). Adar I has no festivals of its own, because all the festivals of Adar move to Adar II, which is the original Adar. Only Rosh Chodesh is observed here, and it runs across two days, Shevat 30 and Adar I 1. The Megillah of Esther is read in Adar II.
- Rosh Chodesh Adar I
- The beginning of the thirteenth month inserted in a leap year; two days of the new month (Shevat 30 and Adar I 1)
Month lengths vary with the type of year, and the Gregorian equivalents are computed by the tool above.