Tayurian Calendar

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The solar Ring of Fire yesterday and last month’s lunar Blood Moon were celestial treats.

As an hobbyist of the calendars of the ancient civilizations (Mayan, Hebrew, Roman, Persian, and of course the 30+ Indian 😏), I could not resist creating a calendar (instead of the usual obligatory Literature Review slide) and including it in my presentation at the NSF Distinguished Lecture:

Dear Dr. Tayur:

Thank you so much for coming to NSF (virtually) on June 7 to be a distinguished lecturer for the directorates for Engineering (ENG), Mathematical and Physical Sciences (MPS), and Computer and Information Sciences (CISE).  We have received many comments from people who enjoyed your presentation and learned a great deal about supply chains. I believe we were all energized by your knowledge and enthusiasm.  I know you are very busy, and I appreciate the time you took.  It was wonderful to meet you.

This slide was in addition to the Quantum Serenity slide that I had previously added in my Distinguished Lecture a few days earlier:

Dear Professor Tayur,

As Koç University College of Engineering, we would like to express our most sincere gratitude to you for giving a seminar at our Distinguished Seminar Series on June 4, 2021.

To show our gratitude, we made a donation to the Educational Volunteers Foundation of Turkey (TEGV) on behalf of you and supported children’s distance education by enabling 4 children to meet with qualified digital education as you can see in the attached documents. 

We sincerely hope that we can invite you in person as well as soon as the world gets back to normal. 

I visited Istanbul and Ephesus in 1998, after a week in Israel visiting Tel Aviv, Jerusalem, Dead Sea, Mossada and driving into Palestine. In a different post, some other time, I will describe some fun exchanges that I have had with the Airport Security folks in Tel Aviv. (Hint: They are not the free-spirit types. 🤷🏽‍♂️)

The Gregorian calendar that we use today (for professional purposes, not to determine religious holidays), a strictly solar calendar, was commissioned by Pope Gregory XIII in the sixteenth century, whose main architect was the Naples astronomer Aloysius Lilius. This new-style calendar differs from its predecessor, old-style Julian calendar, only in that the Julian calendar did not include the century rule for leap years. The Gregorian calendar was later corrected – I believe this was due to Cassini in 1740 – the “1 B.C.E is the year before 1 C.E” problem, as when the Julian (and other calendars such as Coptic) were adopted, they did not know about Zero!

Plutarch writes in Life of Caesar (75 C.E.):

Caesar set out the problem before the best philosophers and mathematicians and, from the methods available, he concocted his own correction that was more precise.

The Julian calendar was proposed by Julius Caesar as a reform to the Roman calendar, and took effect January 1, 45 BC, by edict.

I still can recall, from my high school English class, Shakespeare’s Julius Caesar, Act II, scene I (1623):

Brutus: Is not tomorrow, boy, the ides of March?

Lucius: I know not, sir.

Brutus: Look in the calendar and bring me word.

The Hebrew calendar (4thCentury AD) is more complicated due to its inherent requirement that calendar months be strictly lunar, whereas Passover must always occur in the spring. Because seasons depend on the solar year, like the earlier lunisolar Hindu and Chinese calendars, the Hebrew one must harmonize simultaneously with both solar and lunar events. Indeed, the earliest coherent description of the Hebrew calendar is by al- Khowarizmi (after whom the words algebra and algorithm are coined).

The calculation of the date of Easter (fixed in 325 C.E. by the Council of Nicaea, convened by Constantine the Great) has attracted incredible attention over the centuries:

The first Sunday after the first full moon occurring on or after the vernal equinox.

Depending on the calculations, there were Orthodox Easter, Gregorian Easter, German Protestant Easter, which irritated Johannes Kepler (whose Rudolphine astronomical tables were used by Germans and Swedes):

Easter is a feast, not a planet.

In 1997, the World Council of Churches proposed a uniform date for both the Eastern and Western churches, and from what I can gather, they use a simplified algorithm based on one created by Carl Friedrich Gauss (in 1802, which had an error in its original publication). The Vatican had accepted heliocentrism in 1822, and formally and publicly cleared Galileo of any wrong doing in 1992.

The modern Persian calendar (since 1925, also used in Afghanistan since 1957, but with different month names) is based on a 11thcentury calendar designed by a committee that included the Poet & Quant: Omar Khayyam. 

Don’t even get me going on the Hindu calendars that are mostly lunisolar. The North Indian ones do not agree with the South Indian calendars, and even within the South, the Tamil calendar differs from its neighbors! The most elegant one is solar, by Aryabhatta (Arya Siddhanta, 499 C.E.). I agree entirely – and not surprisingly, also attracted Pierre-Simon Laplace of Traité de mécanique celeste fame to Hindu calendars – with Walther E. van Wijk, Acta Orientala (1924):

Sometimes I cannot help regretting that only so few readers can rejoice with me in the simplicity of his method and the exactness of his results.

The Tayurian Zero is Gregorian 1990, the year I obtained my PhD from Cornell, an escape that I have discussed in Portrait of an Academic Capitalist as a Young Man. I consider the Dark Age as beginning with the publication of Arrow, Harris and Marschak (Econometrica, 1950) – the INFORMS (Inconsequential Formulas? 😊) publications of 1950-1990 had left industry practice unimpacted in 1991 where they were in 1949 – as I have mentioned in Slumming It?, which, turned out to be a (celestial? 😳) gift, as I have laid out in Trillion Dollars of Inventory!

As I was finalizing this post, I received this email:

Dear Sridhar,

First, I want to say thank you for taking the time to spend the day with us. It was very thought provoking and we really enjoyed having a fresh perspective at NSF.

Here is the link to the video-recording (with access passcode 7s9P1f#h).

Kind regards.

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