Friday, March 4, 2011
The Dating of Easter
“Shouldn’t Lent have started already?” a friend asked me last week.
Most years the answer would have been “Yes,” but not this year. This year Ash Wednesday is on March 9, as late as it can be.
The reason is connected with the date of Easter, which in 2011 falls on April 24. Why is that? Odd as it may seem, the celebration of Easter is related directly to the phase of the moon and the spring equinox. Easter is the first Sunday after the first full moon, following the equinox.
The equinox, the first day of spring, happens between the 20th and 23rd of March. This means that in a year when equinox, full moon and Sunday all arrive on March 21st, Easter would be on the 21st. Pushing in the other direction, Easter can fall as late as April 24, which it does this year.
In 2011 spring arrives on Sunday, March 20. The next full moon is on April 18, and the next Sunday is April 24.
Why all these calculations tied to equinox and moon? Aren’t those pagan practices? Why would Christian celebrations be calculated that way?
The answer is tied to the date of Passover. The ancient Israelites’ calendar was a lunar calendar, one that is still in use in modern Jewish practice. In that calendar the date for Passover is determined by moon and equinox. Pesach or Passover is an eight-day long celebration that begins on the night of the fifteenth day of the month of Nissan of the Hebrew calendar, this year April 18. Since the events of Holy Week and Easter coincide with Passover, the early church set the dating of Easter accordingly.
With this explanation one would think that Easter and Passover would always come together. However, they do not. Our present calendar is based on the earth’s rotation around the sun, which divides neatly into 12 months of 30 – 31 days each. The lunar calendar, on the other hand, is based on the revolution of the moon around the earth, 13 months of 28 days. This often results in different positioning of month, equinox and phase of moon, though most years Easter and Passover do fall within a week of one another.
Howard MacMullen © February, 2011