Episode 65: Counting the Days

Starting with this first link, you can get a quick summary of what the history of the calendar looks like. It doesn’t cover nearly as much ground as we do in this episode, but it does give you the basic bullet points.

Similarly, this one goes into a quick read about why there are an unequal number of days in the months.

We use the Gregorian calendar, and if you’re interested in learning some fast trivia about it, here’s six facts you might not known about it that you can have to show off to your friends.

How about the Leap Year? I know we’ve all asked why we have that. So this link will take you to a math-filled read about why we have a Leap Year. Unfortunately, you can’t get rid of the math.

And if you’re looking for a science-heavy read about the Leap Year, then this is the link for you. This one comes from NASA!

And what would happen if we didn’t have a Leap Year? This is another quick read. We have a longer explanation in the episode, but this is just if you want something fast.

This is the BBC article I pulled several quotes from toward the end of the episode when we talked about the places in the world that live in multiple timelines. I only scratched the surface of what the article has in it so I’d really encourage you to read the whole thing.

Here is a slideshow of the images I showed M and Karen during this episode. Under the pictures is a numbered list that gives you a full explanation for each image so you know what you’re looking at! You can see the images on our Instagram and hear us talk about them in the episode, but here you’re getting the details I couldn’t give you in a strictly auditory medium.

In the above slideshow, you’ll see the following:

1. A piece of the Madrid Codex, one of three surviving pre-Columbian Maya books dating to the Postclassic period of Mesoamerican chronology. The Madrid Codex is held by the Museo de América in Madrid and is considered to be the most important piece in its collection. Its content mainly consists of almanacs and horoscopes used to help Maya priests in the performance of their ceremonies and divinatory rituals as well as astronomical tables.
2. This is a reproduction of the Fasti Antiates Maiores. It is a painted wall-calendar from the late Roman Republic, the oldest archaeologically attested local Roman calendar and the only such calendar known from before the Julian calendar reforms. It was created between 84 and 55 BCE. The calendar is a table with thirteen columns, which is a month labelled with an abbreviation. Still legible are IAN for Ianuarius (January), FEB for Februarius (February), APR for Aprilis (April), IVN for Iunius (June), and SEP for September. Each column has several rows containing the days as well as a row indicating the total number of days in the month. Still visible are XXIIX (28) for February, XXIX (29) for April, June and partly for August, XXXI (31) (partial) for May and October. Each day is marked with a letter from A to H, indicating the position of the day in the Roman nundinal cycle, with occasional further letters appended to note the ceremonial category of the day.
3. This is a calendar of the dates of Easter, for the years 532–632. Easter is celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March (a fixed approximation of the March equinox). Determining this date in advance requires a correlation between the lunar months and the solar year, while also accounting for the month, date, and weekday of the Julian or Gregorian calendar. The complexity of the algorithm arises because of the desire to associate the date of Easter with the date of the Jewish feast of Passover which, Christians believe, is when Jesus was crucified. It was originally feasible for the entire Christian Church to receive the date of Easter each year through an annual announcement by the pope. By the early third century, however, communications in the Roman Empire had deteriorated to the point that the church put great value in a system that would allow the clergy to determine the date for themselves, independently yet consistently. Additionally, the church wished to eliminate dependencies on the Hebrew calendar, by deriving the date for Easter directly from the March equinox. Thus, we got this calendar.
4. This is the French Revolutionary Calendar which was created and implemented during the French Revolution, and used by the French government for about 12 years from late 1793 to 1805, and for 18 days by the Paris Commune in 1871, and meant to replace the Gregorian calendar. It was intended to mark the “era of Liberty”, beginning on 14 July 1789, the date of the Storming of the Bastille. Ultimately, the calendar came to commemorate the Republic and not the Revolution. The Common Era, commemorating the birth of Jesus Christ, was abolished and replaced with l’ère républicaine, the Republican Era, signifying the “age of reason” overcoming superstition, as part of the campaign of dechristianization. The First Republic ended with the coronation of Napoleon I as Emperor.
5. This is the month of June from the Très Riches Heures du Duc de Berry or in English The Very Rich Hours of the Duke of Berry. It’s made by the Limbourg brothers between 1412 and 1416 and is illumination on vellum. It was painted using rare and costly pigments and gold and is the most famous and possibly the best surviving example of manuscript illumination in the International Gothic style. There is a lot of info about this set, and you can see the full thing and read all about it here on the Wiki!
6. This is the Ishango bone. It dates to the dates to the Upper Paleolithic era. This is a picture of it on exhibition at the Royal Belgian Institute of Natural Sciences. M mentioned the bone right at the beginning of the episode as being a potential period tracker. It’s believed to be either a lunar calendar or a tally stick of some other kind, and one of the theories is that it might have been a menstrual tracker, but in any case, at 20,000 years old, it is possibly the oldest mathematical tool of mankind, and it is almost surely made by women.
7. Finally, the only other oldest calendar system we possibly have is the Lebombo Bone at 40,000 years old or so. It’s made of a baboon fibula with incised markings discovered in Border Cave in the Lebombo Mountains located between South Africa and Eswatini. According to The Universal Book of Mathematics the Lebombo bone’s 29 notches suggest “it may have been used as a lunar phase counter, in which case African women may have been the first mathematicians, because keeping track of menstrual cycles requires a lunar calendar”.