Friday the 13th: Only 2 in Leap Year

 This photograph shows the late children's television host, Fred Rogers, with the
hand-puppet King Friday the 13th, used to prevent children's superstitions. Today
(and every Friday the 13th) is the birthday of King Friday the 13th, the monarch
of the "Neighborhood of Make-Believe" since 1966 on the popular, national children's
television program, "Mister Rogers' Neighborhood," produced by WQED-TV channel 13 
in Pittsburgh. Originally, when WQED-TV premiered in 1954 as the nation's first
community-sponsored, educational television station, King Friday the 13th had been
the king of time on the "Children's Corner" television program's "Calendarland" (hence,
why all royal family names are days-of-the-week !).
(Image Source: Fred Rogers Productions)

By Glenn A. Walsh

Reporting for SpaceWatchtower

Despite the superstition that revolves around the date of Friday the 13^th, it is true that the 13^th day of the month occurs slightly more often on a Friday, than any other day of the week in the Gregorian Calendar.

Today, 2020 November 13, is the second of two occurrences of Friday the 13^th in 2020. The other occurrence this year was in March. There were only two occurrences of Friday the 13^th this year, because 2020 is a leap year.

The last time Friday the 13^th occurred in November, in 2015, it was the third of three occurrences of Friday the 13^th—the most number of such occurrences possible in one calendar year. Of course, the reason there were three such occurrences in 2015 is because the first occurred in February. And, during a non-leap year, the February calendar of days-of-the-week is always repeated in March (then adding days 29, 30, and 31), and then again in November (which also added days 29 and 30), due to the fact that February has precisely four weeks in non-leaps years.

On average, Friday the 13^th occurs once every 212.35 days. Any month that begins on a Sunday includes a Friday the 13^th. Every calendar year includes at least one Friday the 13^th. And, the longest period that can occur without a Friday the 13^th is fourteen months: from July to September of the following year which is a non-leap year or from August to October of the following year which is a leap year.

Over the 400-year recurring cycle of the Gregorian Calendar (which contains 146,000 normal days, 97 leap days, 20,871 weeks, and 4,800 months), the number of occurrences of the 13^th day of the month on each of the seven days of the week is the following:

Friday – 688

Sunday – 687

Wednesday – 687

Monday – 685

Tuesday – 685

Thursday – 684

Saturday – 684

The superstition surrounding Friday the 13^th may have originated in the Middle Ages, with the Biblical story of Jesus' Last Supper where 13 individuals were present, and his Crucifixion the next day, a Friday. One individual present at the Last Supper, Judas (perhaps considered the 13th), would betray Jesus.

Friday, 1307 October 13, the date King Philip IV of France supposedly arrested hundreds of the Knights Templar, may have also contributed to the superstition, but not until the 20^th century (although the documentation of this story is quite limited).

The publication of a novel in 1907, Friday the Thirteenth by Thomas W. Lawson, may have popularized the superstition. The novel depicts a Wall Street broker using the superstition to create a financial panic on a Friday the 13^th.

Friday the 13^th is not the unlucky day in other cultures. In Spanish-speaking countries, Tuesday the 13^th is unlucky, partly due to the fall of Constantinople occurring on Tuesday, 1204 April 13. In Italy, Friday the 17^th is the unlucky day, with Italians actually considering the number 13 as lucky; more recently, with American and European influences, some Italians now also consider Friday the 13^th as unlucky.

However, confirmation bias is considered by psychologists as the reason the Friday the 13^th superstition has lasted so long. People remember bad things that happen on a Friday the 13^th, while forgetting the other occurrences of Friday the 13^th when nothing spectacular happens.

Internet Links to Additional Information ---

 
More on Friday the 13th ---
Mathematics: Link >>> http://scienceworld.wolfram.com/astronomy/FridaytheThirteenth.html
General: Link >>> https://en.wikipedia.org/wiki/Friday_the_13th
History -
   Link 1 >>> http://www.todayifoundout.com/index.php/2013/09/the-origin-of-friday-the-13th-as-an-unlucky-day/
   Link 2 >>> http://www.snopes.com/luck/friday13.asp

How Mister Rogers Made Friday the 13th Less Scary:
Link >>> http://nowiknow.com/how-mr-rogers-made-friday-the-13th-less-scary/

More on King Friday XIII:
Link >>> https://en.wikipedia.org/wiki/Neighborhood_of_Make-Believe#Regular_puppets

More on "Mister Rogers' Neighborhood" & the "Neighborhood of Make-Believe":
Link >>> https://en.wikipedia.org/wiki/Mister_Rogers'_Neighborhood

"The Sky Above Mister Rogers' Neighborhood," a planetarium show produced by Family Communications, Inc. (now The Fred Rogers Company) and the Henry Buhl, Jr. Planetarium and Observatory at Pittsburgh's Carnegie Science Center:
Link >>> https://carnegiemuseums.org/magazine-archive/2003/mayjun/feat5.htm

More about WQED-TV channel 13, the nation's 1st community-sponsored TV station:
Link >>> https://en.wikipedia.org/wiki/WQED_%28TV%29

More on November 13: Link >>> https://en.wikipedia.org/wiki/November_13

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.                Originally published Friday, 2015 November 13. Updated & re-published Friday, 2020 November 13.

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gaw

Glenn A. Walsh, Informal Science Educator & Communicator:
< http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
SpaceWatchtower Editor / Author: < http://spacewatchtower.blogspot.com/ >
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: < http://www.planetarium.cc >

Buhl Observatory: < http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html >

* Adler Planetarium, Chicago: < http://adlerplanetarium.tripod.com > 

* Astronomer, Educator, Optician John A. Brashear: < http://johnbrashear.tripod.com > 

* Andrew Carnegie & Carnegie Libraries: < http://www.andrewcarnegie.cc >