Editing Leap year (section)

==Hebrew calendar==<!-- This section is linked from [[Jewish holiday]] -->
The Hebrew calendar is lunisolar with an [[embolismic month]]. This extra month is called ''Adar Rishon'' ([[Adar 1|first Adar]]) and is added before ''[[Adar]]'', which then becomes ''Adar Sheini'' ([[Adar 2|second Adar]]). According to the [[Metonic cycle]], this is done seven times every nineteen years (specifically, in years 3, 6, 8, 11, 14, 17, and 19). This is to ensure that [[Passover]] ({{Transliteration|he|''Pesah''}}) is always in the spring as required by the [[Torah]] (Pentateuch) in many verses<ref>Exodus 23:15, Exodus 34:18, Deuteronomy 15:1, Deuteronomy 15:13</ref> relating to Passover.

In addition, the Hebrew calendar has postponement rules that postpone the start of the year by one or two&nbsp;days. These postponement rules reduce the number of different combinations of year length and starting [[Week-day names|days of the week]] from 28 to 14, and regulate the location of certain religious holidays in relation to the [[Shabbat|Sabbath]]. In particular, the first day of the Hebrew year can never be Sunday, Wednesday, or Friday. This rule is known in Hebrew as "{{Transliteration|he|''lo adu rosh''}}" ({{lang|he|לא אד״ו ראש}}), i.e., "Rosh [ha-Shanah, first day of the year] is not Sunday, Wednesday, or Friday" (as the Hebrew word {{Transliteration|he|''adu''}} is written by three [[Hebrew alphabet|Hebrew letters]] signifying Sunday, Wednesday, and Friday). Accordingly, the first day of Passover is never Monday, Wednesday, or Friday. This rule is known in Hebrew as "{{Transliteration|he|''lo badu Pesah''}}" ({{lang|he|לא בד״ו פסח}}), which has a double meaning&nbsp;— "Passover is not a legend", but also "Passover is not Monday, Wednesday, or Friday" (as the Hebrew word {{Transliteration|he|''badu''}} is written by three Hebrew letters signifying Monday, Wednesday, and Friday).

One reason for this rule is that [[Yom Kippur]], the holiest day in the Hebrew calendar and the tenth day of the Hebrew year, now must never be adjacent to the weekly Sabbath (which is Saturday), i.e., it must never fall on Friday or Sunday, in order not to have two adjacent Sabbath days. However, Yom Kippur can still be on Saturday. A second reason is that [[Hoshana Rabbah]], the 21st day of the Hebrew year, will never be on Saturday. These rules for the Feasts do not apply to the years from the Creation to the deliverance of the Hebrews from Egypt under Moses. It was at that time (cf.&nbsp;Exodus 13) that the God of Abraham, Isaac and Jacob gave the Hebrews their "Law" including the days to be kept holy and the feast days and Sabbaths.

Years consisting of 12&nbsp;months have between 353 and 355&nbsp;days. In a {{Transliteration|he|''k'sidra''}} ("in order") 354-day year, months have alternating 30 and 29&nbsp;day lengths. In a {{Transliteration|he|''chaser''}} ("lacking") year, the month of [[Kislev]] is reduced to 29&nbsp;days. In a {{Transliteration|he|''malei''}} ("filled") year, the month of [[Marcheshvan]] is increased to 30&nbsp;days. 13-month years follow the same pattern, with the addition of the 30-day Adar Alef, giving them between 383 and 385&nbsp;days.