Medieval Writing
Reading a Calendar (2)
calendar page Calendar page from a 15th century book of hours produced in Flanders for the English market (National Library of Australia MS 1097/9, f.4r), by permission of the National Library of Australia.
This shows a fairly standard format for a late medieval calendar page. The month is July. The more important festivals are entered in rubric, and it can be seen that they include such general ones as the Visitation, Thomas the apostle and Mary Magdalen. They also include St Thomas of Canterbury, a saint with particular significance to the English.
The gold initials at the top of the page are KL for kalens, the first day of the month in the Roman calendar. On the 7th row of the actual calendar, to the left of the rubric for St Thomas of Canterbury, the abbreviated term Nos stands for nones, the Roman dating term which refers to either the 5th or the 7th day, depending on the month. On the 15th day the abbreviation Id stands for ides.

Down the left are two rows, one of Roman numerals and the other of letters. These are part of a fiendishly cunning method of calculating the date of Easter in any given year. Concentrate carefully now. The numbers are called the Golden Numbers and every year has a Golden Number. To find the Golden Number for any given year, take the number of the year, add 1, divide by 19 and work out the remainder. If the remainder is 0 the Golden Number is 19. (The following example is snaffled from Wieck 1988, as I would probably end up getting the arithmetic wrong!)

eg. for the year 1524

1524 + 1 = 1525

1525 ÷ 19 = 80, remainder = 5 (Remember, they didn't have pocket calculators.)

v = Golden Number for 1524

The letters, A to G constantly repeated, are called the Dominical Letters and are used to identify the Sundays of any given year. Each year has a Dominical Letter, and calculating it is real fun. The year is added to a quarter of itself, with the remainder ignored; this sum is divided by 7 and the remainder from this operation is subtracted from 3 or else from 10 in order to produce a positive integer. The number then corresponds to a Dominical Letter.

eg. back to the year 1524

1524 + (1524 ÷ 4) = 1524 + 381 = 1905

1905 ÷ 7 = 272, remainder = 1

3 - 1 = 2 2 = Dominical Letter B

Right, now we have the basic data with which to search our calendar. Easter must fall on the first Sunday after the first full moon which follows the spring equinox, which means that it can be no earlier than 22nd March and no later than 25th April. The Golden Number represents the new moon, so we search for that number between 1st March and April 12th, count forward 14 days to the full moon, then look forward again to the next appearance of the Dominical letter, and that date is Easter Sunday. Easter Sunday for 1524 was on 27th March.

These days, of course, you can cheat and just look it up in Cheney 1970 or do a quick fix on the web at the English Calendar or the Medieval Calendar Calculator sites. The last will even give you the Golden Number and the Dominical Letter of the year for good measure. If you want to get technical about it, you can investigate the Easter Dating Method site.
Calculating the date of Easter was a highly significant matter for the Christian church, but the letters and numbers have a broader significance through the annual cycle. The Golden Numbers effectively relate the lunar calendar to the solar calendar throughout the year and the phases of the moon can be calculated from them. The Dominical letters also indicate Sundays throughout the year.
Some books of hours simplified the process by providing tables which gave the Golden Number and the Dominical Letter for each year, for the benefit of patrons who weren't so good at arithmetic, and even included the date of Easter for each year. However, all this is an exposition rather than an explanation and leaves a couple of important questions unanswered. How did they come up with these arithmetical computations and why did they have such a complicated system for working out when to hold their most important festival of the year?
Scholars of the early Christian church devoted much time and energy to methods of calculating the date of Easter, given it had to be held at the appointed time in relation to the lunar calendar. The mode of calculation was subject to various controversies, but was ultimately based on methods developed in Alexandria where they were expert at astronomy. However, methods for performing the actual computations were thrashed out in various works known as computistical texts. It was important to get it right because it had become a matter of church authority to ensure that it was celebrated on the same date throughout western Christendom. Great mental energy was expended on this problem.
computational diagram
Long expositions, computations and esoteric complicated diagrams are found in these works, such as this one from the late 11th century (British Library, Cotton Caligula A XV, f.125v). By permission of the British Library.
Why they did it this way is based in history, symbolism and church authority. In the very earliest days of the Christian church there had been a diversity of practice in relation to the celebration of Easter among various branches of the church. The short answer to the difficulty was that it was decided at the Council of Nicea in 325 that Easter was to be celebrated on the Sunday following the full moon after the spring equinox. This was by no means the end of the story, as there were still divergent ways of actually computing the date, but they eventually got it under control by the 6th century.
The reason for using the lunar calendar is based in the origins of Christianity as an offshoot of the Jewish religion. The Jewish calendar was lunar, with various untidy solutions to keep it synchronised with actual astronomical events. The major feast of the Jewish calendar, the Passover or Pasch, at which the paschal lamb was sacrificed, was calculated from this lunar calendar. This ritual also required that the first fruits of the corn be brought to the priests, so if it fell too early before the corn was ripe an extra month was inserted to take it past the spring equinox.
The earliest Christians continued to follow the Jewish rituals and the symbolic association of the sacrifice of the paschal lamb with the sacrifice of Christ, the lamb of God, tied these two feasts together. However, at some stage and not without divergences of practice, Sunday became the appropriate day for celebrating the Resurrection of Christ, so that it was not celebrated on the feast of the Pasch but on the first Sunday after. While the Christians eventually developed their own method of computing the date, it was forever tied to its origins in the Jewish faith. Its retention in a completely different calendrical system to that used for everything else occurs to this day.
Easter Sepulchre
The Easter Sepulchre in Patrington church, Yorkshire, depicts the Resurrection and was used in the rituals of Easter.
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