INTRODUCTION
The Jewish calendar is an ancient and complex system reflecting both the lunar months and solar years as well as the seasons and crop growth in the Land of Israel. It guides us through the cycles of the year, and also aids our recollection of significant historical moments in our history. So, for example, during Pesach we may watch the wheat ripen and also recall that God redeemed us from slavery in this season.
Zionist pioneers, who were largely secular, noted that the Jewish religious calendar reflected the climate of our original homeland and used this calendar for agriculture. They may not have recognized that this calendar, which they embraced for practical purposes, was an indispensable thread weaving through the tapestry of our identity and heritage. Today it is both the civil and religious calendar in Israel, alongside the Gregorian calendar.
DAYS
The Jewish day begins at sunset per the account of creation in Breisheet. “There was setting, there was dawning, day one.” Holidays last from evening to evening. The days of the week are numbered: First Day (א) being Sunday and Seventh Day being Saturday, or Shabbat.
The length of the days and the hours vary by season. Days are longer in summer and shorter in the winter, so the hours of each day vary accordingly. In determining the times of prayer, an hour is one-twelfth of the time between sunrise and sunset.
A new day starts after sunset or when three stars are visible in the sky. (This would have occurred earlier in ancient times, when there was no light pollution obscuring our view of the heavens.) Twilight, the liminal time between the moment the sun disappears below the horizon and the moment three stars are visible in the sky, is called, בֵּין הַשְׁמָשׁוֹת, meaning ‘between the two suns.’ Shabbat is observed from before dark on Friday until after dark on Saturday to ensure that we do not unintentionally violate its proscriptions.
WEEKS
The seven-day cycle of weeks continues regardless of months, seasons, or years, and every seventh day is a Sabbath of rest, during which we emulate God by refraining from creative work.
Every seventh year is considered a Sabbatical year, and today, some farms in modern Israel observe both Sabbatical and Jubilee years even though Rabbi Abraham Isaac Kook ruled that this is no longer required.
MONTHS
The months are determined by the new moons and the years are dictated by the position of the earth relative to the sun. Since there are twelve months in the Jewish year, but a lunar month is less than thirty days, the twelve months do not add up to a solar year of three hundred and sixty five days. To ensure it is in sync with both the sun and the moon, some years have an additional month inserted into them, and two particular months may vary between twenty nine or thirty days.
Months begin when the first sliver of the new moon is visible, around sunset. The moon waxes for about two weeks until it is full. After it is full, the moon wanes for about two more weeks until it becomes invisible for approximately two days. Then the next new lunar crescent appears.
In ancient times, the Sanhedrin would declare a new month after two eyewitnesses had seen the lunar crescent between midday and midnight. Although members of the Sanhedrin were well versed in astronomy and had mathematical models to correctly predict when the new moon would appear, the verse in Shemot, “This month shall be unto you the beginning of months,” was understood to mean people were responsible for witnessing and consecrating the new moon. Witnesses would appear in pairs and be questioned individually. If their testimony was accepted, the new month was declared. Specific questions were asked to verify their testimony.
The decision to add a leap month was based on observation of natural agriculture-related events. The earliest known calculation for determining when to add a leap month was introduced around 358 CE, but was revised in the 10th century after a debate between the rabbis of the Holy Land and Babylon.
The synodic month is 29½ days. So, to ensure the calendar remains in sync with the actual phase of the moon, a calendar month is sometimes twenty-nine days long and sometimes thirty. The first day of the month and the thirtieth day of a full or malei month, are called Rosh Chodesh, the “Head of the Month,” and are a semi-festal.
There are twelve lunar months, alternating between 29 and 30 days. The first month, Nisan, has 30 days and the next month, Iyyar, has 29. The number of days alternates between 30 and 29 each month throughout the year, until Cheshvan or Kislev. Following those two months, Tevet always has 29, Shevat 30, and Adar 29.
Nisan 30 days
Iyyar 29 days
Sivan 30 days
Tammuz 29 days
Av 30 days
Elul 29 days
Tishrei (New Year) 30 days
Cheshvan 29 or 30
Kislev 29 or 30
Tevet 29 days
Shevat 30 days
(Adar Alef 30 days)
Adar/AdarBet 29 days
An extra day may be added to Cheshvan or removed from Kislev to prevent Yom Kippur from falling on a Friday or Sunday or to prevent Hoshannah Rabbah from falling on Shabbat. Both months can be 29 days, both can be 30 days, but if Cheshvan has 29 days, then Kislev must have 30. (Yom Kippur cannot fall on a Friday or Sunday, or there would be two consecutive days when preparing food and burying the dead are prohibited, Hoshana Rabbah cannot occur on Shabbat, or we could not carry a lulav on the holiday.)
The new moon of Tishrei is significant because it is the primary determiner of the date of Rosh HaShanah, the new year. Rosh HaShannah begins on the first day of Tishrei. On the evening following 29 Elul, the court would sanctify the day as the first of Tishrei. If witnesses appeared the next day, the day could be retroactively established as Rosh HaShannah. If witnesses did not appear, then the following day would be Rosh HaShannah and retroactively, the previous evening would be a regular weekday. To prevent people from treating the first day lightly, it was decided that Rosh Hashannah would be celebrated as a two-day holiday.
Each Rosh Chodesh (new moon) is a holiday for women because oral tradition says that when the Israelites who had just left Egypt created a golden calf to worship during Moses’s absence, the Israelite women refused to participate in its creation or worship. In ancient times, women rested from work during the new moon.
Most Jewish festivals begin during the full moon, the fifteenth day of the month. At this time, the moon is at its brightest and rises at sunset.
Originally, we named the months as we do the days of the week: first month, second month, and so on, starting with Nisan, the month God redeemed us from Egypt. After we returned from the Babylonian captivity, we adopted Babylonian names for the months to remind us that God redeemed us a second time.
LEAP MONTHS
As mentioned earlier, a year of 12 lunar months is shorter than a solar year, it is 354 days rather than 365. To ensure that Pesach is observed in the springtime near the equinox, a leap month is added seven times every 19 years. (Every 19 years, the phases of the moon recur on the same day of the year.)
In ancient times, Adar Bet was added to a year based on astronomical events and observation of the ripening barley and fruit on trees. If spring had not arrived, a second Adar was added. Since today’s calendar is based on mathematical calculations, Adar Alef is now considered the extra month.
SEASONS
The autumn and winter months (Elul through Shevat) are called the Days of Rain. The spring and summer months (Adar through Av) are called the Days of Sun. Prayers for rain are included in the liturgy beginning at the end of Sukkot. The three pilgrimage festivals of Sukkot, Pesach, and Shavuot occur during spring, summer, and autumn.
YEARS
There are four new years in the Hebrew calendar: the first of Nisan, for measuring a king’s reign and marking the beginning of pilgrimages, the First of Elul, for the tithing of animals, the First of Tishrei, the birthday of the world, and Tu B’Shevat, for measuring the age of trees.
YEAR AND EPOCH
In the Middle Ages, Maimonides codified earlier calendrical calculations. He also changed the naming of the epoch. No longer do we date events “since the Destruction of the Temple.” Now the epoch is “since the Creation of the world.” (Anno Mundi 1 is the year before creation.)
HOLY DAYS
Following is a list of the holidays on the Hebrew calendar. With the exception of Chanukah and modern Israeli holidays, most these days are described in The Torah.
The month of Tishrei, The Tribe of Efraim (Libra)
1-2 Rosh HaShannah
3 Tzom Gedaliah
Shabbat Shuvah
10 Yom Kippur
15 Festival of Sukkot (Gate of Earth)
21 Hoshana Raba
22 Sh’mini Atzeret and Simchat Torah
The month of Cheshvan, The Tribe of Menasheh (Scorpio)
7 Yom HaAliyah
11 Rachel’s Yahrtzeit
29 Sigd
The month of Kislev, The Tribe of Binyamin (Sagitarius)
24-2 Chanukkah
The month of Tevet, Tribe of Dan (Capricorn)
10 Asara B’Tevet
The month of Shevat, The Tribe of Asher (Aqaurius)
Shabbat Shirah
15 Tu B’Shevat
The month of Adar Alef, The Tribe of Levi
(Leap month)
The month of Adar/Adar Bet, The Tribe of Naftali (Pisces)
Shabbat Shekalim
Shabbat Zachor
13 Taanit Ester
14 Purim
Shabbat Parah
Shabbat HaChodesh
The month of Nisan, The Tribe of Yehuda (Aries)
Days of Sun begin!
Shabbat HaGadol
14 Taanit Bechorot
15-21 Festival of Pesach (Gate of Sea)
16 Begin Omer count
22 Mimouna
27 Yom HaShoah
The month of Iyyar, The Tribe of Yissachar (Taurus)
Continue Omer count
3 Yom HaZikaron
4 Yom HaAtzmaut
15 Pesach Sheini
18 Lag B’Omer
29 Yom Yerushalayim
The month of Sivan, The Tribe of Zevulun (Gemini)
6 Festival of Shavuot (Gate of Sky)
The month of Tamuz, The Tribe of Reuven (Cancer)
17 Tzom Tammuz
The month of Av, The Tribe of Shimon (Leo)
Shabbat Chazon
9 Tisha B’Av
Shabbat Nachamu
15 Tu B’Av
The month of Elul, The Tribe of Gad (Virgo)
Days of Rain begin!
20 Leil Selichot
MODERN HOLY DAYS
After the festival of Pesach, three holy days cascade over us in rapid succession: Holocaust Remembrance Day, Memorial Day for Fallen Soldiers and Victims of Terror, and Israel’s Independence Day. These new observances were declared after the creation of the modern state of Israel. Their observance will be moved if their dates fall on or adjacent to Shabbat.
Another modern observance occurs shortly after those. Yom Yerushalayim celebrates Israel’s regaining control over Jerusalem nineteen years after Jordan conquered the city, expelled all Jews, and destroyed the Jewish Quarter.
CELESTIAL EVENTS
Cross Quarter Day (Lughnasad) Av (or Elul) near Tu B’av
Autumn Equinox Tishrei (or Elul) near New Moon of Tishrei
Cross Quarter Day (Samhain) Cheshvan (or Kislev) near Rachel’s Yahrzeit
Winter Solstice Tevet (or Kislev) near New Moon of Tevet
Cross Quarter Day (Imbolc) Shevat (or Adar Alef) near Tu B’Shevat
Vernal Equinox Adar (or Nisan) near New Moon of Nisan
Cross Quarter Day (Beltaine) Iyyar (or Nisan) near Lag B’Omer
Summer Solstice Sivan (or Tammuz) near New Moon of Tammuz
THE ZODIAC AND THE TWELVE TRIBES
Ancient astronomers divided the sky (and the year) into twelve equal sections. Later, the Israelites associated these twelve regions with the twelve tribes of Israel.
The Twelve Tribes of Israel originated with the thirteen children of the Four Holy Mothers: Bilhah, Rachel, Zilpah, and Leah (ברז׳׳ל). Bilhah was the mother of Dan and Naftali. Rachel was the mother of Yosef and Binyamin. Zilpah was the mother of Gad and Asher. Leah was the mother of six sons, Reuven, Shimon, Levi, Yehudah, Issachar, Zevulun, and one daughter, Dinah.
The half-tribes of Efraim and Menasheh were descended from the two children of Yosef. (Isaac never stopped playing favorites.) Yosef’s wife, Asnat, may have been the daughter of Dinah, making these tribes descendants of both Leah and Rachel. The Levites were appointed priests and given no portion in the Land.
The Twelve Tribes lived in the following regions of the Land:
Gad - East bank of the Jordan River
Efraim - Center
Menasheh - Both sides of the Jordan River
Binyamin - Southern center
Dan - Coastal center
Asher - Coastal north
Levi (no portion in the Land)
Naftali - North
Yehuda - South
Yissachar - Northern center
Zevulun - North
Reuven - East bank of the Jordan River
Shimon - South, within the portion of Judah
THE "SEVEN SPECIES" OF THE LAND
The Hebrew calendar was an agricultural calendar. Holidays, especially the pilgrimage festivals, were determined by agricultural cycles. Seven crops were particularly valued by the ancient Israelites and Judeans:
Grapes, harvested in Elul and Tishrei
Figs, harvested in Elul and Tishrei
Olives, harvested in Cheshvan
Barley, harvested in Nisan and Iyyar
Wheat, harvested in Sivan
Pomegranates, harvested in Tammuz and Av
Dates, harvested in Av, Elul, and Tishrei
CONCLUSION
The Hebrew calendar and the Hebrew language, as much as the knowledge of our sacred texts, are essential for us to live as a people in our Land. It is a cornerstone of Jewish identity and heritage, connecting Jews across generations.
The Hebrew calendar weaves together threads of history, faith, community, and life in the Land. It reminds us of our shared history, guiding us through the cycle of the year, its produce, holy days, and modern commemorations. It provides a roadmap to our future, anchoring our aspirations within a traditional framework.
As early Zionist pioneers discovered almost 200 years ago, the Hebrew calendar is essential for living in the Land. It is second only in importance to the revival of the Hebrew language. The Hebrew language, along with the Hebrew calendar and the Torah and Talmud, form the bedrock of Jewish culture, enabling us to preserve, transmit, and transform our beliefs, values, and customs from one generation to the next. Without this calendar, our connection to our history, our faith, and our Land would be greatly diminished.
The Hebrew calendar and the Hebrew language are unifying forces, sources of strength and unity that reinforce our sense of purpose as a people. Whether it’s the the reading of the weekly Torah parasha on Shabbat, the introspection of Yom Kippur, the joyous observance of the Passover seder, or the grief and pride of Yom HaZikaron, or the quiet joy of watching twinkling Chanukkah lights, the Hebrew calendar keeps us rooted in our Land, offering us a sense of belonging and continuity. The calendar doesn’t just mark time. It marks the heartbeat of the Jewish people and guides us into the future.
