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This template shows a variety of information about the Hebrew calendar year.

==Default behavior==
{{tl|Hebrew year}} without a parameter provides information on the current [[Hebrew calendar]] year, ''[[Anno mundi|AM]]'' {{#timel:xjY}}.

==Parameters==
The only allowed parameter is {{para|1|nnnn}} (or simply {{para||nnnn}}), where nnnn is a Hebrew calendar year (as ''anno mundi''—years since creation). 
*See below for comments on appropriate values to use.

==General comments==
{{main|Hebrew calendar#Modern calendar{{!}}Hebrew calendar (Modern calendar)}}

The fixed Jewish calendar now in use is attributed to the sage [[Hillel II]] in the mid-fourth century CE. While some scholars disagree with that notion, it ''is'' commonly agreed that:
* During the era of the [[Second Temple]] (as late as first century CE), an observational version of the calendar was in use, not the fixed version in use today.<ref>Whether there was a calculated version supporting the observational version is beyond the scope of this brief description.</ref>
* By about the ninth century CE, the current calendar (without the ''anno mundi'' year numbering) was in place.
Accordingly, any use of the calendar (or this template) earlier than the calendar's establishment — whenever that might have been — must be viewed as [[proleptic calendar|proleptic]].

This template is not designed to be used for dates earlier than ''AM (Anno mundi)'' 1, and does not work properly for such dates. Similarly, while this template will continue to calculate cycles for dates far into the future, it is not clear how meaningful such information would be for years later than ''AM'' 6000.<ref>See [[Year 6000]] for a description in classical Jewish sources as to what potentially happens after that. Alternatively, see {{slink|Hebrew calendar|Astronomical calculations}} for a discussion of seasonal drift in the Hebrew calendar and the likelihood that at some point correction would be required.</ref>

==Outputs==
===''Anno mundi'' year number===
Year numbers used by this template, both as input and output, are based on the ''[[Anno Mundi]]'' ("years since creation") year numbering tradition currently in use (Note that other year numbering systems [epoch dates] were more commonly used than this as late as the tenth century CE).

For Gregorian year "yyyy", the corresponding Hebrew year is "(yyyy + 3760)" before Rosh Hashanah (in September or October), and "(yyyy + 3761)" thereafter.
* As an example, this Gregorian year is ''{{#time:Y}},'' so it corresponds to Hebrew year ''{{#time:Y|+3760 years}}'' until Rosh Hashanah, then ''{{#time:Y|+3761 years}}'' after Rosh Hashanah.

===Fixed points on the calendar (''keviyah'')===
Because of specific rules about the calendar calculations, the day-of-the-week configuration of any year's calendar can be completely described with three pieces of information. Traditionally, this is done one of two ways:

* Day-of-week for Rosh Hashanah, characterization of year as [[Hebrew calendar#Deficient, regular, and complete years|deficient, regular or complete]], and day-of-week for Passover
* Day-of-week for Rosh Hashanah, characterization of year as deficient, regular or complete, and whether the year is regular (12-month) or intercalated (13-month)

The first approach is used here.<ref>The traditional description using three Hebrew letters for this purpose was not included here to reduce the coding burden. Further information is available on that at [[:he:הלוח העברי#אורך השנה וקביעת ימי השבוע שלה|Hebrew Wikipedia]] or [[:yi:קביעות פון א יאר|Yiddish Wikipedia]].</ref> These three pieces of information are sufficient to show whether a year is regular or intercalated. However, that information is included explicitly in the next section as well, as the year of the ''machzor katan'' actually determines whether the year is regular or intercalated.

There are fourteen legal configurations of the calendar, seven for regular years and seven for intercalated years.

''These calculations are driven by a [[#Subtemplate and limitations|subtemplate]] (<includeonly>[[</includeonly>/rhdatum<includeonly>]]</includeonly>).''

===Small cycle and leap years (''machzor katan'')===
The Torah requires that Jewish months be calculated based on new moon cycles;<ref>See, ''e.g.,'' {{bibleref||Exodus|12:1|HE}} ''ff.''</ref> at the same time, it requires Passover to be in "the month of the spring".<ref>{{bibleref||Exodus|23:15|HE}}</ref> Accordingly, the Jewish calendar must reconcile both lunar and solar components; it is a [[lunisolar calendar]]. 

The 19-year small/lunar cycle (''machzor katan'') is the Hebrew calendar's embodiment of the [[Metonic cycle]], which reconciles lunar cycles with solar years. According to the Metonic cycle, seven lunar months must be added (intercalated) during every 19 solar years to an otherwise lunar calendar to keep the lunar and solar calendars aligned. In the current Hebrew calendar, the extra month is added in years 3, 6, 8, 11, 14, 17 and 19, and these years of the cycle are identified as "leap years". All other years are identified as "not leap years".

* The count of small cycles is proleptic.
* The identification of specific years as "leap" or "not leap" is also proleptic. Prior to the adoption of the fixed calendar, the Sanhedrin could and did use a variety of criteria to determine if any specific year should be intercalated. 
* For years far in advance of the adoption of the fixed calendar, it is probably more accurate to approximate the date of Passover by assuming it fell on the first full moon day following the northward equinox, using astronomical data.

===Great cycle (''mchzor gadol'') and ''Birkat Hachama''===
The 28-year Great/solar cycle (''machzor gadol'') is based on the calendar of [[Samuel of Nehardea|Mar Shmuel]], which is identical to the [[Julian calendar]]. In a universe where the Julian calendar exactly describes a solar year, if solar year 1 is defined to start on Sunday evening at 6:00 pm, solar year 2 will begin 1.25 days later in the week (at midnight from Monday to Tuesday), solar year 3 a further 1.25 days later (Wednesday at 6:00 am), and so forth. It is not until the beginning of year 29 that another year starts on a Sunday evening at 6:00 pm. Accordingly, tradition states that the universe is "back to its original configuration" after 28 years. To honor that, [[Birkat Hachama]] is recited each 28 years on the Wednesday morning following the (Julian) northward equinox, because the sun was created on "the fourth day" (Wednesday).<ref>{{bibleref||Genesis|1:14|HE}}</ref><ref>Why the custom of Birkat Hachama is based on the tradition of a spring creation and not a Rosh Hashanah creation is beyond the scope of this brief description.</ref> Accordingly, the first year of each 28-year cycle is identified as a year when Birkat Hachama is recited.

* It was known even in the days of Mar Shmuel that the length of a year was shorter than 365.25 days. An explanation as to why the blessing was nevertheless tied to this calculation is beyond the scope of this brief description. However, it is clear that the calculation of this cycle is symbolic, and proleptic.

===Sabbatical year cycle (''Shmita'') and tithing ===
The Torah specifies that the land is to lie fallow every seven years.<ref>See, ''e.g.,'' {{bibleref||Exodus|23:10-11|HE}}</ref> The year when that happens is known as the sabbatical year, in Hebrew ''shevi'it'' ("seventh") or ''[[shmita]]'' ("release"). The Torah additionally specifies that the [[second tithe]] be separated during years 1, 2, 4 and 5 of the seven-year cycle, while the [[poor tithe]] is to be separated during years 3 and 6 of the cycle. Accordingly, this template outputs information related to this cycle.

* Calculation of this cycle during years that the [[Temple in Jerusalem]] was standing is complicated by inclusion of the [[Jubilee (biblical)|Jubilee year ''(yovel)'']] cycles. Output of this section is therefore suppressed for years prior to the destruction of the Second Temple.

==Subtemplate and limitations==
Calculations on this template are driven by a subtemplate (<includeonly>[[</includeonly>/rhdatum<includeonly>]]</includeonly>) that contains Gregorian dates for the first day of [[Rosh Hashanah]]. These were sourced from Hebcal.com.<ref>http://www.hebcal.com</ref> At present, only dates going back to 1752 CE have been included, because Hebcal.com does not take into account the Julian-to-Gregorian calendar conversion/"correction", so is based on the [[proleptic Gregorian calendar]], not the Julian calendar in general use prior to the conversion. (See [[Adoption of the Gregorian calendar]] and [[Old Style and New Style dates]].) Similarly, only dates going forward to about ''AM'' 6000 (2239–2240 CE) are included, because the applicability of the calculations to dates much past that is uncertain. (See [[#General comments|above]].)

==References==
{{Reflist}}

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