The Mystery of the Missing Months

                    https://commons.wikimedia.org/wiki/File:Stonehenge_on_27.01.08.jpg

With November on the way, I decided to look into a question that has bothered me for some time: Why are the months out of sync with the numbers referenced by their Latin roots?

For November the Latin root of it refers to nine, just like October refers to eight and December to 10. So how did it end up as the 11th out of a dozen?

The most comprehensive answer to this puzzling question is to be found in an article posted last year on Live Science. One theory is that the original calendar had only 10 months, and so November was rightly placed as the penultimate month. The mismatch of name and placement only resulted from the addition of January and February to start out a calendar that had begun in March. 

Another theory is that the Roman Empire did use a calendar of 12 months. However, while New Year’s Day was set for March, some places would start their year in January. While that may sound odd, the article points out that businesses frequently set their fiscal calendars to begin in a month other than January. 

You can read through the whole article to decide which theory you find more compelling.

Related:    http://uncommoncontent.blogspot.com/2013/04/happy-early-birthday-shakespeare.html

Once in a Blue Moon

Super Moon image from https://commons.wikimedia.org/wiki/File:Supermoon.jpg

Tonight we will have a Super Moon, as we will next month and the month after that. But the third one is special because it  will also be lined up for a lunar eclipse. But wait, that's not all that's special about the January 31, 2018 full moon. It falls under the designation of a Blue Moon -- at least in one sense. 

"Once in a blue moon." How often is that? about every 2 1/2 years, though whether you'd say 2.5 or 2.7  depends on which definition you use for blue moon, .

From the time I looked it up some years ago, I considered the blue moon to refer to the second full moon in a solar calendar month. (Obviously, lunar calendars are designed to have only a single full moon in a month). However, today I looked it up and found that it also had another meaning that is a bit more precise, though not as commonly used today.

From https://www.space.com/15455-blue-moon.html

The older meaning defines a Blue Moon as the third full moon in a season that has four full moons. Called a seasonal Blue Moon, this occurs about every 2.5 years, according to NASA. Why the third moon? There are roughly 29.5 days between full moons, making it unusual for two full moons to fit into a 30- or 31-day-long month. 

Accordingly, what fits a blue moon definition in one sense may not fit it another. The seasonal blue moon last occurred on May 21, 2016. But a blue moon measured by month rather than by season can only occur at the very end of the month, and that is said to occur about every 2.7 years.

Here's the infographic from: https://www.space.com/16776-blue-moon-explained-infographic.html

This particular terms has evolved into multiple meanings that deviate quite a bit from the strictly astronomical.  Space.com link brought me to : http://www.skyandtelescope.com/observing/once-in-a-blue-moon/, which traces the terms through various meanings, including some specific to songs. The earliest it finds is an expression of absurdity that then came to mean never:

like saying the Moon is made of green cheese. Both were obvious absurdities, about which there could be no doubt. "He would argue the Moon was blue" was taken by the average person of the 16th century as we take "He'd argue that black is white."

 The concept that a blue Moon was absurd (the first meaning) led eventually to a second meaning, that of "never." The statement "I'll marry you, m'lady, when the Moon is blue!" would not have been taken as a betrothal in the 18th century.

 Then there were times when the moon actually appeared blue, as a result of huge amounts of ash in the air from volcanoes or fires.

So, by the mid-19th century, it was clear that visibly blue Moons, though rare, did happen from time to time — whence the phrase "once in a blue Moon." It meant then exactly what it means today, a fairly infrequent event, not quite regular enough to pinpoint. That's meaning number four, and today it is still the main one.

However, from an astronomical point of view, the blue moon did come to mean something more specific, though the way we tend to use it today -- the definition I taught my own kids -- seems to find its roots only as far back as the 20th Century. 

One striking fact for those of us who are familiar with lunar calendars is how the frequency of blue moons dovetails with leap months, namely 7 times in every 19 year cycle. The Chinese calendar adds a leap month about once every 3 years, and the the Jewish calendar is set to haves 7 leaps years every 19 years.   

Happy (early) birthday, Shakespeare

I was wondering about April 23rd really being Shakespeare's birthday, given the shift from the Julian to the Gregorian calendar. I found that addressed at bloggingtherenaissance.blogspot.com

In fact, we don't have a record of Shakespeare's birth, though we do have one of his christening on April 26, 1564. The assumption is that he was born 3 days before that.  

However, April 23rd of 1564 was a date based on the Julian calendar. What's the effect of the shift to the Gregorian calendar?

The Julian calendar was made up of 365 1/4 days a year. It defined the dates of Europe from the days of Julius Caesar in 45 BCE through 15821 adding up to ten extra days by that time.  

That changed in 1852 when  Pope Gregory XIII reformed the calendar, subtracting those ten days with a massive leap forward. That year the day after October 4th was designated October 15th.  Talk about losing time!

England being England, though, and not considering itself subject to Catholic rule, adhered to the Julian calendar for nearly two more centuries. It only adopted the Gregorian calendar in 1752. 

By then an additon day was added on January 1, 1700. A day was also added 100 years later and 100 years after that. However, there was no additional day added in 2000.

According to the calculations of that blog, Shakespeare's April 23rd birthday actually translates into a May 3rd birthday in the Gregorian calendar.