Fernsler has traveled the country over the last decade lecturing on triskaidekaphobia, the fear of the number 13. He said he became interested in the subject in 1987, the last year in which the dreaded day occurred three times.
A professor at Wilson College in Chambersburg, Pa., at the time, Fernsler said the number 13 kept popping up in his life.
For instance, he said he stepped on his bathroom scale and his weight registered 169. That might mean little to the average person, but to a math teacher, it is instantly recognized as the 13th multiple of 13.
"It was fairly insignificant things like that. I just kind of got interested," he said.
So Fernsler set about to document the history of the date.
Butch Cassidy was born on a Friday the 13th in April 1866. So was Cuban dictator Fidel Castro, in August 1926.
Other Friday the 13th moments:
-- April 13, 1928 - the first live television broadcast into a private home.
-- Oct. 13, 1995 - the 500 millionth guest at Walt Disney World.
-- Friday, Nov. 13, 1789, was the date on Benjamin Franklin's famous letter coining the "death and taxes" phrase.
Fernsler's research has included famous triskaidekaphobes. Napoleon, J.P. Getty and Herbert Hoover all were deathly afraid of the number 13, he said. A skeptical Mark Twain apparently became convinced when he attended a dinner party as the 13th guest. A friend had begged him not to go, and when he returned, Twain told his chum that 13 is indeed bad luck: There was only enough food for 12.
Perhaps the most superstitious of all, however, was Franklin D. Roosevelt. Fernsler said the FDR kept his personal secretary close at hand during dinner parties in case a last-minute cancellation or addition threatened to bring the number of guests to 13.
Roosevelt also ordered the train to leave at 12:10 a.m. on the 14th or 11:50 p.m. on the 12th to avoid having to depart for a trip on the 13th day of a month.
Roosevelt died on April 12, 1945, a few hours before the 13th.
"It was almost like he said, 'Well, I'm leaving on my final journey, so I'm not going to go on the 13th,'" Fernsler said.
There is even a mathematical rationale for the fear of Friday the 13th, sort of.
S.R. Baxter wrote an academic paper in 1969 determining that the 13th day of the month falls on Friday more often than on any other day. He was 13 when he wrote the paper.
The origins of fear of 13 dates back centuries. Fernsler said many triskaidekaphobes point to the Last Supper, at which there were 13 guests. Jesus was crucified on a Friday, a day that came to be known as "Hangman's Day."
The fear may have other divine inspiration, Fernsler said. He pointed to Nordic mythology in which an evil god named Loki crashed a party of 12 other gods and killed Balder, the most popular god.
In Hagerstown, police and firefighters are putting the Friday the 13th emergency plan into effect.
OK, not really.
"It's just another day for us," Hagerstown Police Department Capt. Robert Hart said.
Actually, officials from both departments said a full moon poses far more problems.
But that's another story.