Passover

==Date and duration==
{{see also|Hebrew calendar|Yom tov sheni shel galuyot}}
The Passover begins on the 15th day of the month of [[Nisan]], which at present falls between March 26 and April 25 of the [[Gregorian calendar]].<ref>See [[Jewish and Israeli holidays 2000–2050]] for more information.</ref> The 15th day begins in the evening, after the 14th day, and the seder meal is eaten that evening. Passover is a spring festival, so the 15th day of Nisan typically begins on the night of a [[full moon]] after the northern [[March equinox|vernal equinox]].<ref>{{cite web|url=http://www.meteor.wisc.edu/~hopkins/dstreme/97easter.htm|title=Full Moon, Easter & Passover|website=University of Wisconsin|first=Edward J.|last=Hopkins|year=1996|access-date=April 10, 2017|archive-date=June 7, 2018|archive-url=https://web.archive.org/web/20180607170345/http://www.meteor.wisc.edu/~hopkins/dstreme/97easter.htm|url-status=live}}</ref> However, due to [[Intercalation (timekeeping)|leap months]] falling after the vernal equinox, Passover sometimes starts on the second full moon after vernal equinox, as in 2016.

To ensure that Passover did not start before spring, the tradition in ancient Israel held that the [[Lunar new year#Middle East/West Asia|lunar new year]], the first day of Nisan, would not start until the barley was ripe, being the test for the onset of spring.<ref>The barley had to be "eared out" (ripe) in order to have a wave-sheaf offering of the first fruits according to the Law. {{cite book |title=Secrets of Time |last=Jones |first=Stephen |year=1996}} This also presupposes that the cycle is based on the northern hemisphere seasons.</ref> If the barley was not ripe, or various other phenomena<ref>"..., when the fruit had not grown properly, when the winter rains had not stopped, when the roads for Passover pilgrims had not dried up, and when the young pigeons had not become fledged. The council on intercalation considered the astronomical facts together with the religious requirements of Passover and the natural conditions of the country." – {{Cite book | last=Spier | first=Arthur | title=The Comprehensive Hebrew Calendar | year=1952 | publisher=Behrman House, Inc. | location=New York}}, p.&nbsp;1</ref> indicated that spring was not yet imminent, an intercalary month ([[Adar II]]) would be added. However, since at least the 4th century, the intercalation has been fixed mathematically according to the [[Metonic cycle]].<ref>"In the fourth century, ... the patriarch [[Hillel II]] ... made public the system of calendar calculation which up to then had been a closely guarded secret. It had been used in the past only to check the observations and testimonies of witnesses, and to determine the beginning of the spring season." – Spier 1952, p.&nbsp;2</ref>

In [[Israel]], Passover is the seven-day holiday of the Feast of Unleavened Bread, with the first and last days celebrated as legal holidays and as holy days involving holiday meals, special prayer services, and abstention from work; the intervening days are known as [[Chol HaMoed]] ("Weekdays [of] the Festival"). Jews outside of Israel celebrate the festival for eight days. [[Reform Judaism|Reform]] and [[Reconstructionist Judaism|Reconstructionist]] Jews usually celebrate the holiday over seven days.<ref>{{cite web| last1= Shapiro| first1= Mark Dov| title= How Long is Passover?| url= http://www.sinai-temple.org/passover/length.php| website= sinai-temple.org| publisher= Sinai Temple| access-date= April 9, 2015| archive-date= April 7, 2015| archive-url= https://web.archive.org/web/20150407194507/http://www.sinai-temple.org/passover/length.php| url-status= live}}</ref><ref>{{cite web|url=http://www.reformjudaism.org/passover-7-or-8-days|last1=Dreyfus|first1=Ben|title=Is Passover 7 or 8 Days?|website=ReformJudaism.org|publisher=Union for Reform Judaism|access-date=April 9, 2015|archive-date=April 8, 2015|archive-url=https://web.archive.org/web/20150408015041/http://www.reformjudaism.org/passover-7-or-8-days|url-status=live}}</ref><ref>{{cite web |url=http://www.rabbinicalcollege.edu.au/holidays/passover/pesach_cdo/aid/871715/jewish/What-Is-Passover.htm |title=What Is Passover? |publisher=Rabbinical College of Australia and N.Z. |access-date=March 17, 2012 |archive-date=August 5, 2012 |archive-url=https://archive.today/20120805110640/http://www.rabbinicalcollege.edu.au/holidays/passover/pesach_cdo/aid/871715/jewish/What-Is-Passover.htm |url-status=dead }}</ref> [[Karaite Judaism|Karaites]] use a different version of the Jewish calendar, differing from that used with modern Jewish calendar by one or two days.<ref>{{cite book|title=Calendar and Community: A History of the Jewish Calendar 2nd Century BCE – 10th Century CE|first=Sacha|last=Stern|page=viii|publisher=Oxford University Press|year=2001|isbn=0198270348}}</ref> The [[Samaritans]] use a calendrical system that uses a different method from that current in Jewish practice, in order to determine their timing of feastdays.<ref>Reinhold Pummer,''The Samaritans,'' [[Wm. B. Eerdmans Publishing]], 2016 {{isbn|978-0802867681}}, pp. 7, 258ff.</ref> In ''2009'', for example, Nisan 15 on the Jewish calendar used by [[Rabbinic Judaism]] corresponds to April 9. On the calendars used by Karaites and Samaritans, ''Abib'' or ''Aviv'' 15 (as opposed to 'Nisan') corresponds to April 11 in ''2009''. The Karaite and Samaritan Passovers are each one day long, followed by the six-day Festival of Unleavened Bread – for a total of seven days.<ref>{{cite book|title=1,001 Questions and Answers on Pesach|page=291|first=Jeffrey M.|last=Cohen|isbn=978-0853038085|year=2008|publisher=Vallentine Mitchell }}</ref>