Moveable feasts - ancient and modern

Derwent Water and snowy Skiddaw

A further week of revisions began on March 11th, and then I was quite ill for a couple of weeks. I feel a bit like Suzanne in The Boy with Two Heads who, by Easter, was coming out of her coma and asking whether the hospital was real. I wasn't as ill as Suzanne, but I am suddenly aware that it is both April Fools' Day and Easter Monday today. (It is also extremely cold, in spite of wall to wall sunshine in Cumbria - minus three degrees Centigrade at night!) So an immovable feast and a moveable feast fall on the same day.

I am gently amused by the fact that in 2013 I am not the only one still confused over why our Easter is when it is. In the UK and most of the western Christian world it was yesterday. But in Christian Orthodox countries like Russia and Greece it will be on May 5th. It seems that we still haven't been able to agree on this point in spite of more than 2,500 years' deliberation as to when the lengthening of the days and the hope of new beginnings should be marked each year.

Niko Lang's diagram from Wikipedia

In the ancient Hellenic world, by 500 or so BC, some astronomers had already understood that the Earth was a sphere. They believed, however, that the sun, moon, planets and stars revolved around it. This is called the geocentric (Earth centred) system as opposed to the heliocentric (sun centred) system that we now know to be the case. They made careful observations and fairly accurate predictions of the sun’s equinoxes and solstices, as well as the normal phases of the moon and planets, and even some eclipses (“Herodotus, … who lived in the 5th century BC, cited that Thales (ca. 624-547 BCE), the Greek philosopher, predicted the solar eclipse of 28 May 585 BCE …”).

In Ancient Athens, as in most city states, the timing of religious festivals varied from year to year (see my page called Measuring time in Ancient Athens), and were arranged to take into account these differing movements of the sun and moon.

Stonehenge, June 21st 2005 (Wikipedia)

But even then, the equinoxes and solstices provided an incontrovertible structure upon which to hang the more moveable feasts.*

Strangely, we can be more fickle today.

In present-day western Christian churches (Anglican, Catholic, Methodist, and many others), Easter is set according to a formula based on the Gregorian calendar, as the Time and Date website states:

“In 325CE, the Council of Nicaea established that Easter would be held on the first Sunday after the first full moon occurring on or after the vernal equinox. From that point forward, the Easter date depended on the ecclesiastical approximation of March 21 for the vernal equinox. Easter is delayed by one week if the full moon is on a Sunday.”

This year the full moon after the equinox was on Wednesday, March 27th. The first Sunday after that was yesterday, March 31st, Easter Sunday in 'the west'. 

However, Greek and most other Orthodox Christian Churches use the older and less accurate Julian calendar to set the date of Easter (though not always, confusingly, of Christmas). The Julian Calendar decrees that the vernal equinox falls 13 days later than it really does, on April 3^rd. Through some calculation I am unable to verify, this results in Greek Orthodox Easter falling on May 5^th this year, 2013.

So a large part of our modern Christian world manages to be less accurate in the timing of a moveable feast that depends upon an equinox, than those pagan and 'unsophisticated' Ancients...

* In case, like me, you are not 100% clear about such things, the equinoxes are the days when the sun is above the horizon for 12 hours resulting in day and night having equal length (usually March 21st and September 21st). The solstices are the days that are either the longest (June 21st) or the shortest (December 21st) in the year. In the Southern Hemisphere the solstices are the other way round.