How Are Medieval Calendars Numbered?
Calendars during the middle ages and earlier were not numbered sequentially (1-30 or 31) as we do today, rather each day was numbered reverse sequentially in relation to 3 important days: Kalends, Nones, and Ides. Generally speaking, Kalends was the 1st day of the month, Nones was the 5th day of the month and ides was the 13th of the month. It is easy to find these dates if we look UCR 012V (Februarius). On the top left hand side of the calendar we have a blue “K” and a red “L”, this “KL” is an abbreviation of Kalends and appears on the top left of every calendar rather than the word written out next to the first date, unlike the other two days. In the fifth row under the “KL” in the red column the word “Nonas” (or Nones) is written and in the 13th row the word “idibus” (or ides) is written, and it can be inferred that the next Kalends is on March 1st.
So, rather than the dates being numbered sequentially they are numbered backwards from the next of these three dates, the dates themselves being included in these counts. So let’s number the dates from Kalends (the first date/row under the large “KL”) to Nones (the 5th date/row under the large “KL”). Again we need to work backwards in order to do this, so let’s start with Nones, rather than this date being labeled the 5th it would be labeled 1 Nones, the date above it (the 4th) would be 2 Nones (notated on this calendar as II NO), the 3rd would be 3 Nones (III NO), the 2nd would be 4 Nones (IIII NO). We then reach Kalends (Februrary 1st) and the numbering starts over again with 1 Kalends (I KL). This notation is done throughout the rest of the calendar so February 11th would be 3 Ides (III ID), the 17th would be 13 Kalends (XIII KL) and the 28th would be 2 Kalends (II KL).
While it is typical from Kalends to land on the 1st, Nones on the 5th and Ides on the 13th this is not always true. If we look at UCR 013R (Marcius), this calendar does not adhere to that pattern (this observance is also true of the months of May, July and October; See Poole “The Days of the Month”). In this calendar, Nones lands on the 7th of the month and Ides on the 15th of the month. However the method is still the same, the date is numbered reverse sequentially based upon it relation to the nearest of these three important days. Thus, instead of March 2nd being 4 Nones as it was above for February, it would instead be 6 Nones (notated VI N here) because it is 5 days before Nones. Even though Nones and Ides might move slightly depending upon the month, it is important to note that Kalends always lands on the first and Ides is always eight days after Nones.
Note: It has been determined that it takes 365 ¼ Solar days of 24 hours for the Earth to rotate around the Sun, however the Solar Year (as we demonstrate it in calendars) has been divided into 365 Solar Days. Thus every four year we insert an extra day in February in order to make up for the missing time. Every leap year we place this day at the end of February to create February 29th, however with the calendars we are looking at, the bissextum or dies bessextus (The leap day) was inserted before 6 Kalends (VI KL) becoming the new February 24th. Due to the reusability of these calendars, discussed in the next sextion, only feasts or events occurring on the 24th were shifted to now occur on the 25th.
Now that you understand the calendars numbering system, move on to:
But What Day of the Week is it?
Source(s):
Poole, R. L. (1921). The Days of the Month. In R. L. Poole, C. Johnson, & J. Whitney (Eds.), Medieval Reckonings of Time (pp. 23-25). New York, New York: The MacMillan Company.