A moveable feast is an observance in a Christian
liturgical calendar
The liturgical year, also called the church year, Christian year or kalendar, consists of the cycle of liturgical seasons in Christian churches that determines when feast days, including celebrations of saints, are to be observed, and whic ...
which occurs on different dates in different years.
[John Ayto ''Oxford Dictionary of English Idioms'' 2010 p123 019954378X "a movable feast an event which takes place at no regular time. In a religious context a movable feast is a feast day (especially Easter Day and the other Christian holy days whose dates are related to it) which does not occur on the same calendar date each year."]
Spring paschal feasts
Often considered the most important Christian observance, Spring paschal feasts are a fixed number of days before or after
Easter Sunday
Easter,Traditional names for the feast in English are "Easter Day", as in the ''Book of Common Prayer''; "Easter Sunday", used by James Ussher''The Whole Works of the Most Rev. James Ussher, Volume 4'') and Samuel Pepys''The Diary of Samuel ...
, which
varies by 35 days since it depends partly on the
phase of the moon and must be
computed each year. In the
Hebrew calendar
The Hebrew calendar ( he, הַלּוּחַ הָעִבְרִי, translit=HaLuah HaIvri), also called the Jewish calendar, is a lunisolar calendar used today for Jewish religious observance, and as an official calendar of the state of Israel. I ...
, the new moon of
Aviv
Aviv ( he, אביב) means "barley ripening", and by extension "spring season" in Hebrew. It is also used as a given name, surname, and place name, as in Tel Aviv. The first month of the year is called the month of Aviv in the Pentateuch. The mo ...
, spring, is fixed as the
Lunar New Year
Lunar New Year is the beginning of a calendar year whose months are moon cycles, based on the lunar calendar or lunisolar calendar.
The Lunar New Year as a celebration is observed by numerous cultures. It is also named "Chinese New Year" becaus ...
, and the month is called
Nisan
Nisan (or Nissan; he, נִיסָן, Standard ''Nīsan'', Tiberian ''Nīsān''; from akk, 𒊬𒊒𒄀 ''Nisanu'') in the Babylonian and Hebrew calendars is the month of the barley ripening and first month of spring. The name of the month i ...
. The 14 of Nisan is the
paschal full moon An ecclesiastical full moon is formally the 14th day of the ecclesiastical lunar month (an ecclesiastical moon) in an ecclesiastical lunar calendar. The ecclesiastical lunar calendar spans the year with lunar months of 30 and 29 days which are int ...
, the day of the
Pesach seder
The Passover Seder (; he, סדר פסח , 'Passover order/arrangement'; yi, סדר ) is a ritual feast at the beginning of the Jewish holiday of Passover. It is conducted throughout the world on the eve of the 15th day of ,_a_ritual_meal_Haggadah">telling_the_story_of_
,_a_ritual_meal_Haggadah">telling_the_story_of_the_Exodus">Haggadah.html"_;"title="san_in_the_Hebrew_c_...
,_a_ritual_meal_Haggadah">telling_the_story_of_the_Exodus_from_Egypt.__It_is_one_of_the_Three_Pilgrimage_Festivals.html" "title="the_Exodus.html" ;"title="Haggadah.html" ;"title="san in the Hebrew c ...