## The Ides Have It

When my sons woke up today, I told them, “Beware the Ides of March.”

To which Alex responded, “What are ides?”

I explained that the ides are roughly the middle day of the month. But then Alex asked why the ides was the 15th of March instead of the 16th, since March has 31 days.

“I don’t know.”

Nor do I know why the word ides is used to refer to this date. It comes from the Latin word idus, which can be translated to — yep, you guessed it — the English word ides. Nor do I know why ides is singular.

I also don’t know why the ides of March, May, July and October occur on the 15th day, but the ides of every month occur on the 13th day. But it does lead to a fun math problem for a four-year-old to figure out:

What is the maximum number of days between the ides in consecutive months?

Here are some math jokes related to things in the middle:

A circle is a round straight line with a hole in the middle.

What was Zeno of Elea’s middle name?
Of.

And all this talk of ides made me think of a really stupid joke from a really stupid joke book that I read when I was in elementary school. (That was a long time ago, hence the dated references, but maybe some of my older readers will appreciate it.)

If a woman named Ida married Dan Rather, got divorced, then took Bill Knott as her second husband… she’d be Ida Rather Knott.

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• 1. JimsMaher  |  March 17, 2012 at 5:24 pm

In 753 BC, the second King of Rome, Numa Pompilius, promulgated (regulated) Rome’s calendar.

“In Romulus’ time, the calendar had been fixed at 360 days to the year, but the number of days in a month varied from twenty or less to thirty-five or more. Numa estimated the solar year at 365 days and the lunar year at 354 days. He doubled the difference of eleven days and instituted a leap month of 22 days to come between February and March (which was originally the first month). Numa put January as the first month, and may indeed have added the months of January and February to the calendar.” ~http://ancienthistory.about.com/cs/people/a/numapompilius.htm

By design, with such a leap month (also called an intercalary month) the lunar cycle should become periodic with the solar cycle. Approximately, of course. Such that any given phase of the moon should fall on the same date in a given month, every year.

Recall that the lunar cycle is approximately 29.5 days. Figuring the intercalary month was instituted every other year (when not usurped by politicians by adding or removing months out of sequence, for political gain … Ancient Rome is infamous for that stuff).

Then consider that the next calendar reform came under the reign of Julius Caesar in 45 BC.
“Then turning his attention to the reorganisation of the state, he (Julius Caesar) reformed the calendar, which the negligence of the pontiffs had long since so disordered, through their privilege of adding months or days at pleasure, that the harvest festivals did not come in summer nor those of the vintage in the autumn; and he adjusted the year to the sun’s course by making it consist of three hundred and sixty-five days, abolishing the intercalary month, and adding one day every fourth year. Furthermore, that the correct reckoning of seasons might begin with the next Kalends of January, he inserted two other months between those of November and December; hence the year in which these arrangements were made was one of fifteen months, including the intercalary month, which belonged to that year according to the former custom.”
~http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Suetonius/12Caesars/Julius*.html#40

Well, as it turns out the lunar month is closer to 29 days, 12 hours, 44 minutes and 3 seconds. The solar year is closer to 365 days, 5 hours, 49 minutes plus or minus a minute or two … since the earth wobbles at its own frequency and years are measured from specific locations on Earth … we have to include the latitude of the measurement, where the Earth’s wobble was in relation to the beginning of the year being measured, which also means including when in the calendar year that the measured year is to begin. This is assuming the the year itself, with those factors, are a closed system and the gravity of the other planets and other celestial bodies (passing comets, solar winds, and other negligible forces acting on the Solar System at large) have absolutely zero effect on the rate at which the Earth travels around the Sun, which is not the case. So if someone asks you about leap seconds, tell them: “We’re having a party, but don’t get too excited. Blink, and you’ll miss it.”

• 2. venneblock  |  March 20, 2012 at 1:47 pm

Wow! That’s a lot of good info, Jims… Thanks!

The Math Jokes 4 Mathy Folks blog is an online extension to the book Math Jokes 4 Mathy Folks. The blog contains jokes submitted by readers, new jokes discovered by the author, details about speaking appearances and workshops, and other random bits of information that might be interesting to the strange folks who like math jokes.

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