Dating Easter - question from tara_lily
1) Dating of Easter in Modern Times
All the gospel accounts have Jesus being crucified and raised in conjunction with Passover. The Jewish calendar is based in lunar cycles. Like all lunar based calendars you have this pesky problem that the rotation and revolution of the earth aren't nicely aligned and thus the solar year and the lunar calendar don't match. This leads to having the months rotate through the solar year. There are a variety of ways which have been created to fix this problem (in addition to some calendars which don't fix it) as knowing when to plant crops was BIG in the ancient world. The Jewish calendar fixes it by having 235 lunar cycles in 19 years. This means you add an extra lunar cycle (so 13 lunar cycles per year) in years 3, 6, 8, 11, 14, 17, and 19. Because of the way things work, the cycles aren't exactly the same amount of days. (I don't remember exactly how it goes I remember the Babylonian and the Egyptian methods, but not the Jewish one - sorry!)
You can see here for more details about the Jewish calendar.
http://astro.nmsu.edu/~lhuber/leaphist.html
In any case, Passover falls on the 14th day of the month of Nisan, always a full moon and always in the spring. By the third century Christianity was fully organized they were relying on the Jewish Sanhedrin to calculate the date for Easter. This was not acceptable.
There were two opinions on the date of Easter. The Quartodecimians thought Easter should always fall on the first day of the Nisan, the day of the new moon. The day of the week of this date would change with the years. The other group felt that Easter should always be on a Sunday (the day of the week of the Resurrection - the First Day of the Week). In order to confirm a date, break with the Jews, and possibly align the date with a pagan sun festival the council of Nicea stated that Easter was the First Sunday after the First Full Moon following the Spring Equinox (March 21) unless that Full Moon fell on a Sunday in which case Easter would be the following Sunday. At that time they were following the Julian calendar. This was a 12 month calendar that originally followed a correction factor that was not accurate and thus the calendar lost days according to the actual solar calendar (i.e. the predicated date of say an equinox was later than the actual equinox measured by astronomical instruments). There then ensued some local variation based upon Pascal cycles which I am going to ignore because it only caused minor
variations.
The major variation in dates between the Eastern and Western Easters are due to the fact that the West adopted the Gregorian calendar (the one we use today - which is an updated form of the Julian calendar that was in use previously) in the 16th century. This occurred because the Julian calendar looses days (see above) and they had noticed it by the 16th century. The Eastern church has never adopted the Gregorian calendar. Over time the accuracy has been lost. Today the Julian calendar is 13 days off. Thus for the Western Easter the soonest date Easter can occur is March 22 (the last time we saw that date was in the early 1800s and we won't see it again for another 278 years). Because of the difference in calendars the soonest the Easter church can have Easter is March 22 on the Julian calendar or April 4 on the calendars we buy in the stores.
Easters are so drastically different this year because the full moon occurred on March 22nd and the Sunday after that was March 23rd. Since this full moon was too soon for the Eastern calendar that meant that they are very far apart this year. However, ultimately neither calculation of Easter is in any way related to Passover directly and the dates will rotate around one another based on a very complex calculation involving the year of the Jewish cycle (within that 19 year cycle), the full moon, and the day of the week that the full moon
falls on.
2) Issue 2 - difference in days between the gospel accounts.
There are two different sets of dates one in the synoptics (Matthew/Mark/Luke) and one in John. In the synoptic gospels the meal Jesus shares with his disciples is the first Passover Meal. The next day he is crucified. The following day is the Sabbath and then the first day of the new week is the Resurrection. In John, the meal is the night before Passover. Jesus dies on
the cross on the day of Preparation (the evening of which is the first Passover Meal). In this case Jesus literally dies at the point where the Passover lambs are being slaughtered. In this case this day is also the day before the Sabbath. The first day of the week is again the Resurrection.
Here is a little chart (I don't know if it will align correctly in LJ and since I don't know it's not exactly the best graphic - if it doesn't I'll put it on my website). I am using the modern days of the week (where Saturday is the Sabbath) and I am denoting the meals which occur on the evening of the day when discussing the passover to avoid dealing the issue that the Jewish calendar begins the day at sundown.
Day Event
Thurs (Last Supper) Lamb sacrifice/1st Seder (synoptics)
Fri (Crucification) Lamb sacrifice/1st Seder (John)
Sat (In the tomb)
Sun (Resurrection)
All the gospel accounts have Jesus being crucified and raised in conjunction with Passover. The Jewish calendar is based in lunar cycles. Like all lunar based calendars you have this pesky problem that the rotation and revolution of the earth aren't nicely aligned and thus the solar year and the lunar calendar don't match. This leads to having the months rotate through the solar year. There are a variety of ways which have been created to fix this problem (in addition to some calendars which don't fix it) as knowing when to plant crops was BIG in the ancient world. The Jewish calendar fixes it by having 235 lunar cycles in 19 years. This means you add an extra lunar cycle (so 13 lunar cycles per year) in years 3, 6, 8, 11, 14, 17, and 19. Because of the way things work, the cycles aren't exactly the same amount of days. (I don't remember exactly how it goes I remember the Babylonian and the Egyptian methods, but not the Jewish one - sorry!)
You can see here for more details about the Jewish calendar.
http://astro.nmsu.edu/~lhuber/leaphist.html
In any case, Passover falls on the 14th day of the month of Nisan, always a full moon and always in the spring. By the third century Christianity was fully organized they were relying on the Jewish Sanhedrin to calculate the date for Easter. This was not acceptable.
There were two opinions on the date of Easter. The Quartodecimians thought Easter should always fall on the first day of the Nisan, the day of the new moon. The day of the week of this date would change with the years. The other group felt that Easter should always be on a Sunday (the day of the week of the Resurrection - the First Day of the Week). In order to confirm a date, break with the Jews, and possibly align the date with a pagan sun festival the council of Nicea stated that Easter was the First Sunday after the First Full Moon following the Spring Equinox (March 21) unless that Full Moon fell on a Sunday in which case Easter would be the following Sunday. At that time they were following the Julian calendar. This was a 12 month calendar that originally followed a correction factor that was not accurate and thus the calendar lost days according to the actual solar calendar (i.e. the predicated date of say an equinox was later than the actual equinox measured by astronomical instruments). There then ensued some local variation based upon Pascal cycles which I am going to ignore because it only caused minor
variations.
The major variation in dates between the Eastern and Western Easters are due to the fact that the West adopted the Gregorian calendar (the one we use today - which is an updated form of the Julian calendar that was in use previously) in the 16th century. This occurred because the Julian calendar looses days (see above) and they had noticed it by the 16th century. The Eastern church has never adopted the Gregorian calendar. Over time the accuracy has been lost. Today the Julian calendar is 13 days off. Thus for the Western Easter the soonest date Easter can occur is March 22 (the last time we saw that date was in the early 1800s and we won't see it again for another 278 years). Because of the difference in calendars the soonest the Easter church can have Easter is March 22 on the Julian calendar or April 4 on the calendars we buy in the stores.
Easters are so drastically different this year because the full moon occurred on March 22nd and the Sunday after that was March 23rd. Since this full moon was too soon for the Eastern calendar that meant that they are very far apart this year. However, ultimately neither calculation of Easter is in any way related to Passover directly and the dates will rotate around one another based on a very complex calculation involving the year of the Jewish cycle (within that 19 year cycle), the full moon, and the day of the week that the full moon
falls on.
2) Issue 2 - difference in days between the gospel accounts.
There are two different sets of dates one in the synoptics (Matthew/Mark/Luke) and one in John. In the synoptic gospels the meal Jesus shares with his disciples is the first Passover Meal. The next day he is crucified. The following day is the Sabbath and then the first day of the new week is the Resurrection. In John, the meal is the night before Passover. Jesus dies on
the cross on the day of Preparation (the evening of which is the first Passover Meal). In this case Jesus literally dies at the point where the Passover lambs are being slaughtered. In this case this day is also the day before the Sabbath. The first day of the week is again the Resurrection.
Here is a little chart (I don't know if it will align correctly in LJ and since I don't know it's not exactly the best graphic - if it doesn't I'll put it on my website). I am using the modern days of the week (where Saturday is the Sabbath) and I am denoting the meals which occur on the evening of the day when discussing the passover to avoid dealing the issue that the Jewish calendar begins the day at sundown.
Day Event
Thurs (Last Supper) Lamb sacrifice/1st Seder (synoptics)
Fri (Crucification) Lamb sacrifice/1st Seder (John)
Sat (In the tomb)
Sun (Resurrection)