The Jewish lunar year is the basis for Jewish and Christian movable feasts, those annual holidays that do not fall on a fixed date but vary according to astronomical occurrences. Passover fell just before the Crucifixion and Resurrection of Christ, and while the two holidays come together from time to time, like this year, often they do not. For those perplexed by the seemingly random times when Passover and Easter fall on the same dates, here's wading in the weeds to you.
The Jewish calendar year begins in the Fall with the celebration of Rosh Hashana. Unlike the Christian solar year, the Jewish calendar uses twelve lunar months of alternating 29 and 30 days. The new moon marks the beginning of each month with the full moon occurring halfway through the month. The seventh month in a normal Jewish calendar year is the month of Nisan. Passover falls on the 14th day of Nisan at the time of the full moon. However, owing to the differences in the solar and lunar calendars, during a Jewish leap year an additional month of 29 days is inserted before the month of Nisan. The extra month realigns the Jewish calendar year with the seasons of the solar year. The Torah commands that Passover be celebrated in the Spring.
The early Christian church was faced with the following conflict in dates: Jesus rose on a Sunday, but Passover can fall on various days of the week. So the early church saw two options: Celebrate Easter in relation to Nisan without regard for the day of the week, or create a system whereby Easter could always be celebrated on a Sunday. That's when the difference between an ecclesiastic full moon and an astronomical full moon came into play, the former determined from ecclesiastical tables. Throw in the conflict between a fixed date for the vernal (Spring) equinox (March 21) versus the actual (meridian) date of the equinox.
The issue was hotly debated and variously practiced during the first centuries of the church. For instance, Easter was celebrated on different days in different places in the same year. The Council of Nicea in 325 A.D. eventually adopted the current system of celebrating Easter on the Sunday following the (Passover or ecclesiastical) full moon after the vernal equinox.
April 4, 2015 - April 11, 2015:
Passover, or Pesach in Hebrew, the holiday commemorating the Hebrews' exodus from slavery in Egypt, lasts seven days in Israel and among Reform Jews, and eight days elsewhere around the world. It begins on the 14th day of Nisan and ends on the 21st of Nisan in Israel (and for Reform Jews) and on the 22nd of Nisan elsewhere.
April 5, 2015:
(Western Churches--Catholic, Protestant)
Easter is calculated as the first Sunday after the Passover full moon that occurs on or after the vernal equinox -- a fixed date of March 21. If the ecclesiastical full moon falls on a Sunday, then Easter is the following Sunday. The holiday can occur anywhere between March 22 and April 25.
April 12, 2015
The Orthodox church bases the date on a slightly different calendar—the Julian calendar instead of the Gregorian. Unlike the Western Church, the Eastern Church sets the date of Easter according to the actual vernal equinox as observed along the meridian of Jerusalem, site of the Crucifixion and Resurrection.
Celebrate our holiest of holidays with joy!
Gerrie Ferris Finger