Editing Hebrew calendar (section)

==Components==
===Days===
{{See also|Zmanim#Evening}}
Based on the classic rabbinic interpretation of {{Bibleverse|Genesis|1:5|HE}} ("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.<ref>{{cite book |url=https://books.google.com/books?id=t8VZga76bw4C&q=%22jewish+day+begins%22+evening&pg=PA169 |title=The Torah For Dummies |first=Arthur |last=Kurzweil |year= 2011 |publisher=John Wiley & Sons |isbn=9781118051832 |via=Google Books}}</ref> Similarly, [[Yom Kippur]], [[Passover]], and [[Shabbat]] are described in the Bible as lasting "from evening to evening".<ref>{{Bibleverse|Leviticus|23:32|HE}}; {{Bibleverse|Exodus|12:18|HE}}; regarding Shabbat ({{Bibleverse|Nehemiah|13:19|HE}}) only the beginning time is mentioned.</ref> The days are therefore figured locally.

[[Halakha|Halachically]], the exact time when days begin or end is uncertain: this time could be either sundown (''shekiah'') or else nightfall (''tzait ha'kochavim'', "when the stars appear"). The time between sundown and nightfall (''bein hashmashot'') is of uncertain status.<ref>{{cite web |title=Zmanim Briefly Defined and Explained |website= chabad.org |url=https://www.chabad.org/library/article_cdo/aid/134527/jewish/Zmanim-Briefly-Defined-and-Explained.htm}}</ref> Thus (for example) observance of [[Shabbat]] begins before sundown on Friday and ends after nightfall on Saturday, to be sure that Shabbat is not violated no matter when the transition between days occurs.

Instead of the [[International Date Line]] convention, there are varying opinions as to where the day changes.<ref>{{cite web |first=Willie |last=Roth |url=http://koltorah.org/ravj/The%20International%20Date%20Line%20and%20Halacha.htm |title=The International Date Line and ''Halacha''  |date=March 1, 2002  |url-status=dead |archive-date=July 18, 2011 |website=koltorah.org |archive-url=https://web.archive.org/web/20110718065425/http://koltorah.org/ravj/The%20International%20Date%20Line%20and%20Halacha.htm }}.</ref><ref>"Appendix II: Baal HaMaor's Interpretation of 20b and its Relevance to the Dateline" in ''Talmud Bavli'', Schottenstein Edition, Tractate ''Rosh HaShanah'', Mesorah Publications Ltd. ("ArtScroll") 1999, where "20b" refers to the 20th page 2nd folio of the tractate.</ref> (See [[International date line in Judaism]].)

===Hours===
{{See also|Zmanim#Relative hours|Relative hour}}
Judaism uses multiple systems for dividing hours. In [[Biblical and Talmudic units of measurement#Day|one system]], the 24-hour day is divided into fixed hours equal to {{frac|1|24}} of a day, while each hour is divided into 1080 ''halakim'' (parts, singular: ''[[helek]]''). A part is {{frac|3|1|3}} seconds ({{frac|1|18}} minute). The ultimate ancestor of the ''helek'' was a Babylonian time period called a ''barleycorn'', equal to {{frac|1|72}} of a Babylonian ''time degree'' (1° of celestial rotation).<ref name=Neugebauer1>{{cite journal|first=Otto |last=Neugebauer|title=The Astronomy of Maimonides and its Sources|journal=Hebrew Union College Annual|volume=23|date=1949|pages=321–363 |jstor=23506591}}</ref> These measures are not generally used for everyday purposes; their best-known use is for calculating and announcing the [[molad]].

In another system, the daytime period is divided into 12 [[relative hour]]s (''sha'ah z'manit'', also sometimes called "halachic hours"). A relative hour is defined as {{frac|1|12}} 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 ([[zmanim]]); for example, the [[Shema]] must be recited in the first three relative hours of the day.<ref>Mishna Berachot 1:2. Note that the mishna specifies that the Shema may be recited "until three hours"; this is understood to mean "until the end of the third hour".</ref>

Neither system is commonly used in ordinary life; rather, the local civil clock is used. This is even the case for ritual times (e.g. "The latest time to recite Shema today is 9:38 AM").<ref>See e.g. [https://www.myzmanim.com/day.aspx?askdefault=1&vars=27526341&q=jerusalem Zmanim: Jerusalem]</ref>

===Weeks===
{{Further|Week#Judaism}}
The Hebrew week ({{lang|he|שבוע}}, {{lang|he-latn|shavua}}) is a cycle of seven days, mirroring the [[creation week|seven-day period]] of the [[Book of Genesis]] in which the world is created.

The names for the days of the week are simply the [[Ordinal number (linguistics)|day number]] within the week. The week begins with Day 1 ([[Sunday]]) and ends with [[Shabbat]] ([[Saturday]]). (More precisely, since days begin in the evening, weeks begin and end on Saturday evening. Day 1 lasts from Saturday evening to Sunday evening, while Shabbat lasts from Friday evening to Saturday evening.)

Since some calculations use division, a remainder of 0 signifies Saturday.

In Hebrew, these names may be abbreviated using the [[Hebrew numerals|numerical value]] of the Hebrew letters, for example {{lang|he|יום א׳}} (''Day 1'', or ''Yom Rishon'' ({{lang|he|יום ראשון}})):
{| class="wikitable" 
|-
! Hebrew name
! Abbreviation
! Translation
! English equivalent
|-
| Yom Rishon (יום ראשון)
| {{lang|he|יום א'}}
| First day
| [[Sunset]] on [[Saturday]] to sunset on [[Sunday]]
|-
| Yom Sheni (יום שני)
| {{lang|he|יום ב'}}
| Second day
| Sunset on [[Sunday]] to sunset on Monday
|-
| Yom Shlishi (יום שלישי)
| {{lang|he|יום ג'}}
| Third day
| Sunset on [[Monday]] to sunset on Tuesday
|-
| Yom Revii (יום רביעי)
| {{lang|he|יום ד'}}
| Fourth day
| Sunset on [[Tuesday]] to sunset on Wednesday
|-
| Yom Hamishi (יום חמישי)
| {{lang|he|יום ה'}}
| Fifth day
| Sunset on [[Wednesday]] to sunset on Thursday
|-
| Yom Shishi (יום שישי)
| {{lang|he|יום ו'}}
| Sixth day
| Sunset on [[Thursday]] to sunset on Friday
|-
| Yom Shabbat (יום שבת)
| {{lang|he|יום ש'}}
| Sabbath day
| Sunset on [[Friday]] to sunset on Saturday 
|}

The names of the days of the week are modeled on the seven days mentioned in the [[Genesis creation myth|Genesis creation account]].<ref>''Hebrew-English Bible,'' {{bibleverse||Genesis|1|HE}}</ref> For example, [[Genesis 1:8]] "... And there was evening and there was morning, a second day" corresponds to ''Yom Sheni'' meaning "second day". (However, for days 1, 6, and 7 the modern name differs slightly from the version in Genesis.)

The seventh day, [[Shabbat]], as its Hebrew name indicates, is a day of rest in Judaism. In Talmudic Hebrew, the word ''Shabbat'' ({{lang|he|שַׁבָּת}}) can also mean "week",<ref>[https://www.sefaria.org/Jastrow%2C_שַׁבָּת.1 Jastrow: שַׁבָּת]</ref> so that in ritual liturgy a phrase like "Yom Reviʻi beShabbat" means "the fourth day in the week".<ref>For example, when referring to the [https://www.sefaria.org/Siddur_Sefard%2C_Weekday_Shacharit%2C_Song_of_the_Day.15?lang=bi&with=all&lang2=en daily psalm recited in the morning prayer].</ref>

====Days of week of holidays====
{{Main|Days of week on Hebrew calendar}}

Jewish holidays can only fall on the weekdays shown in the following table:

{| class="wikitable"
|-style="background-color:#DDDDDD;text-align:center;"
|-
![[Purim]]
![[Passover]]<br />(first day)
![[Shavuot]]<br />(first day)
![[Seventeenth of Tamuz|17 Tammuz]]/<br />[[Tisha B'Av]]
![[Rosh Hashanah]]/<br />[[Sukkot]]/<br />[[Shmini Atzeret]]<br />(first day)
![[Yom Kippur]]
![[Chanukah]]<br />(first day)
![[Tenth of Tevet|10 Tevet]]
![[Tu Bishvat]]
![[Purim|Purim Katan]]<br />(only in leap years)
|-
|Thu||Sat||Sun||Sun*||Mon||Wed
|Sun or Mon
|Sun or Tue
|Sat or Mon
|Sun or Tue
|-
|Fri||Sun||Mon||Sun||Tue||Thu||Mon||Tue||Mon||Tue
|-
|Sun||Tue||Wed||Tue||Thu||Sat
|Wed or Thu
|Wed, Thu, or Fri
|Tue, Wed, or Thu
|Wed or Fri
|-
|Tue||Thu||Fri||Thu||Sat||Mon
|Fri or Sat
|Fri or Sun
|Thu or Sat
|Fri or Sun
|-
|colspan=10| <small>*Postponed from Shabbat</small>
|}

The period from 1 [[Adar]] (or [[Adar II]], in leap years) to 29 [[Marcheshvan]] contains all of the festivals specified in the Bible ([[Purim]], [[Passover]], [[Shavuot]], [[Rosh Hashanah]], [[Yom Kippur]], [[Sukkot]], and [[Shemini Atzeret]]). The lengths of months in this period are fixed, meaning that the day of week of Passover dictates the day of week of the other Biblical holidays. However, the lengths of the months of Marcheshvan and Kislev can each vary by a day (due to the [[#Rosh Hashanah postponement rules|Rosh Hashanah postponement rules]] which are used to adjust the year length). As a result, the holidays falling after Marcheshvan (starting with Chanukah) can fall on multiple days for a given row of the table.

A common mnemonic is "{{lang|he|לא אד"ו ראש, ולא בד"ו פסח}}", meaning: "Rosh HaShana cannot be on Sunday, Wednesday or Friday, and Passover cannot be on Monday, Wednesday or Friday" with each day's numerical equivalent, in [[gematria]], is used, such that א' = 1 = Sunday, and so forth. From this rule, every other date can be calculated by adding weeks and days until that date's possible day of the week can be derived.<ref>{{Cite web |last=Posner |first=Menachem |title=On Which Days Do Jewish Holidays Begin? |url=https://www.chabad.org/library/article_cdo/aid/5504248/jewish/On-Which-Days-Do-Jewish-Holidays-Begin.htm |website=Chabad.org}}</ref>

===Months===
The Hebrew calendar is a [[lunisolar calendar]], meaning that months are based on [[lunar month]]s, but years are based on [[solar year]]s.{{efn|In contrast, the [[Gregorian calendar]] is a pure [[solar calendar]], while the [[Islamic calendar]] is a pure [[lunar calendar]].}} The calendar year features twelve lunar months of 29 or 30 days, with an additional lunar month ("leap month") added periodically to synchronize the twelve lunar cycles with the longer solar year. These extra months are added in seven years (3, 6, 8, 11, 14, 17, and 19) out of a 19-year cycle, known as the [[Metonic cycle]] (See [[#Leap months|Leap months]], below).

The beginning of each Jewish lunar month is based on the appearance of the [[new moon]]. Although originally the new lunar crescent had to be observed and certified by witnesses (as is still done in [[Karaite Judaism]] and [[Islamic calendar|Islam]]), nowadays Jewish months have generally fixed lengths which approximate the period between new moons. For these reasons, a given month does not always begin on the same day as its astronomical conjunction.<ref name=molad>{{cite web |url= http://individual.utoronto.ca/kalendis/hebrew/molad.htm|title=Moon and the Molad of the Hebrew Calendar|last1=Bromberg |first1=Irv|date= August 5, 2010|publisher= utoronto.ca|access-date=July 20, 2019}}</ref>

The mean period of the lunar month (precisely, the [[Months#Synodic month|synodic month]]) is very close to 29.5&nbsp;days. Accordingly, the basic Hebrew calendar year is one of twelve lunar months alternating between 29 and 30 days:<ref name=companion>{{cite book|first1=Bonnie |last1=Blackburn |first2= Leofranc |last2=Holford-Strevens|title=The Oxford Companion to the Year: An Exploration of Calendar Customs and Time-reckoning|publisher= Oxford University Press|date= 2000|pages= 722–725|oclc=216353872}}</ref>

{| class="wikitable"
!colspan="2"| Month number*
!rowspan="2"| Hebrew month
!rowspan="2"| Length
!colspan="2"| Range of possible Gregorian dates{{efn|Valid at least for 1999-2050. In other years, the ranges for Kislev through Adar I may be a bit wider. After 2089 the earliest date for most months will be one day later, and from 2214 the last date will be one day later.}}
|-
! <small>Ecclesiastical/<br />biblical</small> !! Civil 
! First day !! Last day
|-
| style="text-align:center;" | 1 || style="text-align:center;" | 7 || [[Nisan]] || style="text-align:center;" | 30 || style="text-align:center;" | 12 March to 11 April|| style="text-align:center;" | 10 April to 10 May
|-
| style="text-align:center;" | 2 || style="text-align:center;" | 8 || [[Iyar]] || style="text-align:center;" | 29 || style="text-align:center;" | 11 April to 11 May|| style="text-align:center;" | 9 May to 8 June
|-
| style="text-align:center;" | 3 || style="text-align:center;" | 9 || [[Sivan]] || style="text-align:center;" | 30 || style="text-align:center;" | 10 May to 9 June|| style="text-align:center;" | 8 June to 8 July
|-
| style="text-align:center;" | 4 || style="text-align:center;" | 10 || [[Tammuz (Hebrew month)|Tammuz]] || style="text-align:center;" | 29 || style="text-align:center;" | 9 June to 9 July|| style="text-align:center;" | 7 July to 6 August
|-
| style="text-align:center;" | 5 || style="text-align:center;" | 11 || [[Av (month)|Av]] || style="text-align:center;" | 30 || style="text-align:center;" | 8 July to 7 August|| style="text-align:center;" | 6 August to 5 September
|-
| style="text-align:center;" | 6 || style="text-align:center;" | 12 || [[Elul]] || style="text-align:center;" | 29 || style="text-align:center;" | 7 August to 6 September|| style="text-align:center;" | 4 September to 4 October
|-
| style="text-align:center;" | 7 || style="text-align:center;" | 1 || [[Tishrei]] || style="text-align:center;" | 30 || style="text-align:center;" | 5 September to 5 October|| style="text-align:center;" | 4 October to 3 November
|-
| style="text-align:center;" | 8 || style="text-align:center;" | 2 || [[Cheshvan]] (or Marcheshvan) || style="text-align:center;" | 29 (or 30) || style="text-align:center;" | 5 October to 4 November|| style="text-align:center;" | 3 November to 2 December
|-
| style="text-align:center;" | 9 || style="text-align:center;" | 3 || [[Kislev]] || style="text-align:center;" | 30 (or 29) || style="text-align:center;" | 4 November to 3 December|| style="text-align:center;" | 2 December to 31 December
|-
| style="text-align:center;" | 10 || style="text-align:center;" | 4 || [[Tevet]] || style="text-align:center;" | 29 || style="text-align:center;" | 3 December to 1 January|| style="text-align:center;" | 1 January to 29 January
|-
| style="text-align:center;" | 11 || style="text-align:center;" | 5 || [[Shevat]] || style="text-align:center;" | 30 || style="text-align:center;" | 1 January to 30 January|| style="text-align:center;" | 30 January to 28 February
|-
| style="text-align:center;" | 12 || style="text-align:center;" | 6 || [[Adar]] I (only in leap years)|| style="text-align:center;" | 30 || style="text-align:center;" | 31 January to 12 February|| style="text-align:center;" | 1 March to 12 March 
|-
| style="text-align:center;" | 12 || style="text-align:center;" | 6 || [[Adar]] (Adar II in leap years)|| style="text-align:center;" | 29 || style="text-align:center;" | 11 February to 13 March|| style="text-align:center;" | 11 March to 10 April
|-
!colspan=3| Total || 354 (or 353 or 355) <br> 30 days more in leap years!! ||
|-style="background:#FFF;"
|colspan=6 style="text-align:center;"|<small>* – For the distinction between numbering systems, see {{slink||New year}} below.</small>
|}

Thus, the year normally contains twelve months with a total of 354&nbsp;days. In such a year, the month of Marcheshvan has 29&nbsp;days and Kislev has 30&nbsp;days. However, due to the [[#Rosh Hashanah postponement rules|Rosh Hashanah postponement rules]], in some years Kislev may lose a day to have 29&nbsp;days, or Marcheshvan may acquire an additional day to have 30&nbsp;days.

Normally the 12th month is named [[Adar]]. During [[leap year]]s, the 12th and 13th months are named Adar I and Adar II (Hebrew: ''Adar [[Aleph (Hebrew)|Aleph]]'' and ''Adar Bet''—"first Adar" and "second adar"). Sources disagree as to which of these months is the "real" Adar, and which is the added leap month.<ref>[https://dinonline.org/2014/03/03/which-is-the-true-adar/ Which is the true Adar?]</ref>

====Justification for leap months====
The Bible does not directly mention the addition of leap months (also known as "embolismic" or "[[Intercalation (timekeeping)|intercalary]]" months). The insertion of the leap month is based on the requirement that [[Passover]] occur at the same time of year as the spring barley harvest (''aviv'').<ref>{{Bibleverse|Deuteronomy|16:1|HE}}, {{Bibleverse|Exodus|23:15|HE}}; see [https://www.daat.ac.il/he-il/hagim/luach_ivri/%D7%94%D7%9C%D7%95%D7%97-%D7%94%D7%A2%D7%91%D7%A8%D7%99/%D7%A0%D7%A1%D7%A4%D7%97%D7%99%D7%9D/aviv.htm למועד חודש האביב]</ref> (Since 12 lunar months make up less than a solar year, the date of Passover would gradually move throughout the solar year if leap months were not occasionally added.) According to the rabbinic calculation, this requirement means that Passover (or at least most of Passover) should fall after the [[March equinox]].<ref>Talmud, Rosh Hashana 21a; see [https://www.daat.ac.il/he-il/hagim/luach_ivri/%D7%94%D7%9C%D7%95%D7%97-%D7%94%D7%A2%D7%91%D7%A8%D7%99/%D7%A0%D7%A1%D7%A4%D7%97%D7%99%D7%9D/aviv.htm למועד חודש האביב] for elaboration.</ref> Similarly, the holidays of [[Shavuot]] and [[Sukkot]] are presumed by the Torah to fall in specific agricultural seasons.<ref>{{Bibleverse|Exodus|23:16|HE}}, {{Bibleverse-nb|Exodus|34:22|HE}}; {{Bibleverse|Leviticus|23:39|HE}}; {{Bibleverse|Deuteronomy|16:9,13|HE}}</ref>

[[Maimonides]], discussing the calendrical rules in his [[Mishneh Torah]] (1178), notes:
<blockquote>
By 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",<ref>''Hebrew-English Bible'', {{bibleverse||Num|28:14|HE}}.</ref> which implies that we should count the year by months and not by days.<ref name="tcjmwz">[[Mishneh Torah]], Sanctification of the New Moon 1:2; quoted in [https://personal.stevens.edu/~msenator/hand0.pdf Sanctification of the New Moon]. {{webarchive|url=https://web.archive.org/web/20100621084628/http://personal.stevens.edu/~msenator/hand0.pdf |date=2010-06-21 }}. 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.</ref>
</blockquote>

<div style="float:right;margin:10px 0 10px 10px;">{{Hebrew year}}</div>

===Years===
====New year====
[[File:Liten askenasisk sjofar 5380.jpg|right|thumb|A ''[[shofar]]'' made from a ram's horn is traditionally blown in observance of [[Rosh Hashanah]], the beginning of the Jewish civic year.]]

The Hebrew calendar year conventionally begins on [[Rosh Hashanah]], the first day of [[Tishrei]]. However, the Jewish calendar also defines several additional 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 or [[fiscal year]]s", "[[academic year]]s", and so on. The ''[[Mishnah]]'' (c. 200 CE) identifies four new-year dates:

<blockquote>The 1st of Nisan is the new year for kings and festivals. The 1st of Elul is the new year for the [[cattle tithe]], Rabbi Eliezer and Rabbi Shimon say on the first of Tishrei. The [[Rosh Hashanah|1st of Tishri]] is the new year for years, of the [[Shmita]] and Jubilee years, for planting and for vegetables. The 1st of [[Shevat]] is the new year for trees—so the school of Shammai, but the school of Hillel say: On the [[Tu Bishvat|15th thereof]].<ref>[[s:Translation:Mishnah/Seder Moed/Tractate Rosh Hashanah/Chapter 1/1|Rosh Hashanah 1:1]]</ref></blockquote>

Two of these dates are especially prominent:
* 1 Nisan is the ''ecclesiastical new year'', i.e. the date from which months and festivals are counted.<ref>''Hebrew-English Bible,'' {{bibleverse||Exodus|12:2|HE}} "This month [Aviv/[[Nisan]]] shall be unto you the beginning of months; it shall be the first month of the year to you."</ref> Thus [[Passover]] (which begins on 15 Nisan) is described in the Torah as falling "in the first month",<ref>''Hebrew-English Bible,'' {{bibleverse||Leviticus|23:5|HE}}</ref> while [[Rosh Hashana]] (which begins on 1 Tishrei) is described as falling "in the seventh month".<ref>''Hebrew-English Bible,'' {{bibleverse||Leviticus|23:24|HE}}</ref>
* 1 Tishrei is the ''civil new year'', and the date on which the year number advances. This date is known as [[Rosh Hashanah]] ({{lit|head of the year}}).  Tishrei marks the end of one ''agricultural'' year and the beginning of another,<ref>''Hebrew-English Bible,'' {{bibleverse||Exodus|23:16|HE}}, {{bibleverse-nb||Exodus|34:22|HE}}</ref> and thus 1 Tishrei is considered the new year for most agriculture-related commandments, including [[Shmita]], Yovel, [[Maaser Rishon]], [[Maaser Sheni]], and [[Maaser Ani]].

For the dates of the Jewish New Year see [[Jewish and Israeli holidays 2000–2050]].

====Anno Mundi====
{{Main|Anno Mundi}}
[[File:Creation of Light Detail 2.png|right|thumb|The Jewish calendar's reference point is traditionally held to be about one year ''before'' the [[Genesis creation myth|Creation]] of the world.]]

The Jewish year number is generally given by ''{{lang|la|Anno Mundi}}'' (from [[Latin]] "in the year of the world", often abbreviated ''AM'' or ''A.M.''). In this [[calendar era]], the year number equals the number of years that have passed since the [[Genesis creation narrative|creation of the world]], according to an interpretation of [[Biblical]] accounts of the creation and subsequent history. From the eleventh century, ''anno mundi'' dating became the dominant method of counting years throughout most of the world's Jewish communities, replacing earlier systems such as the [[Seleucid era]].<ref name=Jones/><ref>{{Cite book |url=https://books.google.com/books?id=0umDqPOf2L8C&pg=PA87 |title=The Easter Computus and the Origins of the Christian Era |author=Alden A. Mosshammer|year= 2008 |isbn=9780191562365|pages=87–89 |publisher=OUP Oxford }}</ref>
As with {{lang|la|[[Anno Domini]]}} (A.D. or AD), the words or abbreviation for {{lang|la|Anno Mundi}} (A.M. or AM) for the era should properly ''precede'' the date rather than follow it. 

The reference junction of the Sun and the Moon (Molad 1) is considered to be at 5 hours and 204 halakim, or 11:11:20&nbsp;p.m., on the evening of Sunday, 6 October 3761 BCE.<ref>Edgar Frank, ''Talmudic and Rabbinical Chronology: The System of Counting Years in Jewish Literature,'' (New York: Philip Feldheim, Publisher, 1956)</ref> According to rabbinic reckoning, this moment was ''not'' [[Creation according to Genesis|Creation]], but about one year "before" Creation, with the new moon of its first month (Tishrei) called ''molad tohu'' (the mean new moon of chaos or nothing). It is about one year ''before'' the traditional Jewish [[Dating Creation|date of Creation]] on 25 Elul AM 1,{{efn|The significance of 25 Elul derives from Adam and Eve being created on the sixth day of creation, 1 Tishrei AM 2. In this view, AM 2 is the actual first year of the world, while AM 1 is a "placeholder" year, so that calendar dates can be assigned to the days of creation.}} based upon the ''Seder Olam Rabbah''.{{efn|A minority opinion places Creation on 25 Adar AM 1, six months earlier, or six months after the modern epoch.}} Thus, adding 3760 before [[Rosh Hashanah]] or 3761 after to a [[Julian calendar]] year number starting from 1 CE will yield the Hebrew year. For earlier years there may be a discrepancy; ''see [[Missing years (Jewish calendar)]]''.

{{anchor|writing}}In Hebrew there are two common ways of writing the year number: with the thousands, called {{lang|he|לפרט גדול}} ("major era"), and without the thousands, called {{lang|he|לפרט קטן}} ("minor era"). Thus, the current year is written as <span style="direction:rtl;">'''{{lang|he|{{#time:xhxjY}}}}'''</span> &lrm;({{#time:xjY}}) using the "major era" and <span style="direction:rtl;">'''{{lang|he|{{#invoke:string|sub|{{#time:xhxjY}}|3|-1}}}}'''</span> &lrm;({{#expr:{{#time:xjY}}mod1000}}) using the "minor era".

====Cycles of years====
Since the Jewish calendar has been fixed, leap months have been added according to the [[Metonic cycle]] of 19 years, of which 12 are common (non-leap) years of 12 months, and 7 are leap years of 13 months. This 19-year cycle is known in Hebrew as the ''Machzor Katan'' ("small cycle").

Because the Julian years are {{frac|365|1|4}} days long, every 28 years the weekday pattern repeats. This is called the sun cycle, or the ''Machzor Gadol'' ("great cycle") in Hebrew. The beginning of this cycle is arbitrary. Its main use is for determining the time of [[Birkat Hachama]].

Because every 50 years is a Jubilee year, there is a jubilee (''yovel'') cycle. Because every seven years is a sabbatical year, there is a seven-year release cycle. The placement of these cycles is debated. Historically, there is enough evidence to fix the sabbatical years in the [[Second Temple Period]].<ref>B. Zuckermann, ''A Treatise on the Sabbatical Cycle and the Jubilee'', trans. A.&nbsp;Löwy. New York: Hermon Press, 1974.</ref> But it may not match with the sabbatical cycle derived from the biblical period; and there is no consensus on whether or not the Jubilee year is the fiftieth year or the latter half of the forty ninth year.

Every 247 years, or 13 cycles of 19 years, form a period known as an ''iggul'', or the ''Iggul of [[Nahshon ben Zadok|Rabbi Nahshon]]''. This period is notable in that the precise details of the calendar almost always (but not always) repeat over this period. This occurs because the ''molad'' interval (the average length of a Hebrew month) is 29.530594 days, which over 247 years results in a total of 90215.965 days. This is almost exactly 90216 days – a whole number and multiple of 7 (equalling the days of the week). So over 247 years, not only does the 19-year leap year cycle repeat itself, but the days of the week (and thus the days of Rosh Hashanah and the year length) typically repeat themselves.<ref>Nadia Vidro, "The Origins of the 247-Year Calendar Cycle", ''Aleph'', '''17''' (2017), 95–137 [https://doi.org/10.2979/aleph.17.1.0095 doi link].</ref><ref>Dov Fischer, [https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4364371 The Enduring Usefulness of the Tur’s 247-year Calendar Cycle (Iggul of Rabbi Nachshon)]</ref>