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## This Rare Friday the 13th239

Juha-Matti Laurio writes to point out a Washington Times story about how special this particular Friday the 13th is. The digits in the numerical notation for the date add up to 13 — whether you write it in the US or the European form. From the article: "The phenomenon hasn't happened in 476 years, said Heinrich Hemme, a physicist at Germany's University of Aachen who crunched the numbers to find that the double-whammy last occurred Jan. 13, 1520."
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## This Rare Friday the 13th

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• #### I Just Knew I Shoulda Stayed In Bed Today (Score:4, Funny)

on Friday October 13, 2006 @06:23PM (#16431751) Homepage Journal

While the sum of 2+6+1+1+3=13 is mildly interesting, I never thought much about Friday the Thirteenth outside of Pogo [pogopossum.com] strips. Walt kelly's character in the strip, Churchy LaFemme [flickr.com] perhaps more than any other source kept the Friday the Thirteenth fear alive as the turtle fled in horror for decades, long before the series of films arrived. For those of us who remember (and in some cases still read) the strip, it's still a source of amusement.

"Don't shoot! Don't shoot! It's Friday the thirteenth! Very unlucky to get shot on Friday the thirteenth!"

2+6+1+1+4=14, so there goes Saturday the 14th [imdb.com] too.

• #### Re:I Just Knew I Shoulda Stayed In Bed Today (Score:4, Interesting)

on Friday October 13, 2006 @07:28PM (#16432385)
I wonder if Heinrich Hemme's calculations take into account the 10 missing days [navy.mil] in the Gregorian calander between 4 October and 15 October 1582?
• #### Re: (Score:2)

How would his calculations take this into account?

There was no 13th October 1582, so it's irrelevant.

• #### Re: (Score:3, Insightful)

I think that the point of the GP is that it changes when the Fridays are.
• #### Re: (Score:2)

They were only missing in the Catholic world. In England and colonies they didn't switch until 1752, skipping from Sept 2 to Sept 14, although the 13th wouldn't have fallen on a Friday in any case. (Note the extra missing day because of another 170 years of calendar slippage.)

Must have made life interesting in the world between 1582 and 1752. Talk about time zone changes. Travel from Paris to London and arrive a week before you left...

The unix/linux 'cal' program recognizes this, at least for 1752. Might
• #### Re:I Just Knew I Shoulda Stayed In Bed Today (Score:4, Interesting)

on Saturday October 14, 2006 @06:37AM (#16435071)
The really interesting part of the switch, to me, is the Swedish debacle. Essentially, in 1700 they set a 40-year no-leap-days plan to get on track, but ended up with leap days in both of the following leap years, so they ended up one day ahead of the Julian calendar (and still nowhere near the Gregorian calendar). They held a February 30 [wikipedia.org] double leap day in 1712 to get back on Julian and then finally managed to convert to Gregorian by 1753.
• #### Re:I Just Knew I Shoulda Stayed In Bed Today (Score:5, Funny)

on Friday October 13, 2006 @07:32PM (#16432417)
Yeah, and it's amazing that it still adds up to 13 if you switch the numbers around, 1+1+3+2+6 = 13. WOW!
• #### Re:I Just Knew I Shoulda Stayed In Bed Today (Score:5, Informative)

on Friday October 13, 2006 @08:13PM (#16432689)

Vaguely more interesting and almost veering ON topic for slashdot, in binary notation todays date would be

1010 1101 11111010110

...which just so happens to have thirteen "1"s in it.

• #### Re: (Score:2)

My comment was not off-topic. The original post suggests that, by coincidence, the numbers of todays date add up to 13 in both US and European notation, which happens to be just a difference of order.

I was astonished that people actually grasp that gem of mathematical truth.
• #### Re: (Score:3, Informative)

And the hex representation is...

A D 7D6

If you read it like "ADD 7 6" you get 13. I'd look for more examples but I just don't really care. If you're looking for something you will find it everywhere, regardless of what you're looking for.

That is of course unless it's your keys and you're late for work. ad7d6
• #### Re: (Score:2)

Also interesting is that the UNIX timestamp, in binary, also contains 13 1's:

C:\php5>php -r "echo decbin(strtotime('13 Oct 2006'));"
01000101001011110000111101000000
• #### Re: (Score:2)

And like this

0000000 1010 1101 11111010110

it also contains thirteen zeroes.

This is horrible! This must be doomsday!!

No, wait, it's the 14th already...
• #### Re: (Score:2)

"Yeah, and it's amazing that it still adds up to 13 if you switch the numbers around, 1+1+3+2+6 = 13. WOW!"

Unless you get an old COBOL programmer to sum them up for you, in which case you get 11:

06+10+13 = 11

But then the results aren't as fun, which is the life story for COBOL programmers -ducks-.
• #### Commutivity (Score:5, Funny)

<math.induction@gmail.com> on Friday October 13, 2006 @06:23PM (#16431753) Homepage Journal

From TFS:

The digits in the numerical notation for the date add up to 13—whether you write it in the US or the European form.
What a relief! I always suspected that the commutativity of addition [wikipedia.org] applied on both sides of the Atlantic.

Or did they mean to imply that the dæmons who govern paraskevidekatria [wiktionary.org] are too preoccupied to uphold mathematical principles today?

In a related article:

Thirteen people, pledged to eliminate triskaidecaphobia, fear of the number 13, today tried to reassure American sufferers by renting a 13ft plot of land in Brooklyn for 13 cents (10d) a month. (Daily Telegraph, 1967)
• #### Re: (Score:2, Funny)

What a relief! I always suspected that the commutativity of addition applied on both sides of the Atlantic. Or did they mean to imply that the dæmons who govern paraskevidekatria are too preoccupied to uphold mathematical principles today?

If you're in Europe, then you're in luck. It's the 14th already.

• #### Re:Commutivity (Score:5, Funny)

<flippy@example.com> on Friday October 13, 2006 @07:06PM (#16432213) Journal
Speaking of adding:

"The phenomenon hasn't happened in 476 years, said Heinrich Hemme, a physicist at Germany's University of Aachen who crunched the numbers to find that the double-whammy last occurred Jan. 13, 1520."
...someone can't. Or is it 1996? :)
• #### OT: Sig reply (Score:2)

...I'm listening to the guy with the lens in a tube rather than the guy with the corpse on a stick

I hope you are right in the long run, but for immediate, practical purposes, the STICK has more WHACKING heft.

• #### Re: (Score:2)

I hope you are right in the long run, but for immediate, practical purposes, the STICK has more WHACKING heft.

I keep my lart polished and my wrist keen and sharp.
• #### Re: (Score:2)

I dunno. Last tube with a lens in it that I saw would have completely crushed anyone who blundered underneath it. :)

As to the nominal topic... some years ago I was on my way to a SF convention, and the date happened to be Friday the 13th. I stopped at Costco to get a big bag of M&Ms and one other minor item, I forget what. The total turned out to be \$13.13 .... Coincidence? ;)

• #### Re: (Score:2)

... paraskevidekatria ...
Not to be confused with Alkulukuja Paskova Karhu [surfeu.fi], which also deals with the number 13...

• #### Of course, you care about that only if (Score:5, Insightful)

on Friday October 13, 2006 @06:26PM (#16431779)
you're a numerologist, a mystic, a fortune teller or a similar quack. For most other people who happen to be superstitious, it's just another Friday the 13th. And for the rest of us, the overwhelming majority of rational folks, it's just another day...
• #### In other words ... (Score:2)

Most of us don't suffer from Triskaidekaphobia [wikipedia.org]
• #### Mod Parent Down (Score:5, Funny)

on Friday October 13, 2006 @06:29PM (#16431821)
Just to prove to him its not his lucky day.
• #### aahh..but (Score:5, Insightful)

<dadinportland@yah o o .com> on Friday October 13, 2006 @06:57PM (#16432123) Homepage Journal
if it affects how other people behave, then it affects you.

• #### Re: (Score:2)

That's actually my rationale for maybe believing in deities -- they may not exist in any objective sense (I'm agnostic), but other people believe in them, so their behavior is affected, which in turn affects me.
• #### Re: (Score:3, Funny)

And for the rest of us, the overwhelming majority of rational folks, [...]

Wow.

What country do you live in?

Can I come?

• #### Re: (Score:2)

Yeah, but a thunderstorm killed my build server this morning, including the backup drive.

Usually not superstitious.

But this Friday the 13th sucked rocks.
• #### I care about it because... (Score:2)

It's my birthday, you insensitive clod!
• #### 13th Post! (Score:5, Funny)

on Friday October 13, 2006 @06:27PM (#16431791)
sorry....
• #### Re:13th Post! (Score:5, Funny)

on Friday October 13, 2006 @07:07PM (#16432221)
Yep, you hit it. I viewed at -1 Flat, and counted, you are indeed the 13th post.

Congratulations. You have reached the pinnacle of your life.
• #### Re: (Score:2)

"Congratulations. You have reached the pinnacle of your life."

are you kidding me? tomorrow he could be the 14th post.
• #### Re: (Score:2)

are you kidding me? tomorrow he could be the 14th post.

And then? Tomorrow will be the 14th anyway..

• #### Re: (Score:2)

Are you kidding? He's gotta pull off a stunt like that twelve more times. And, for that matter, tweleve more times today.
• #### Pffft.... (Score:5, Funny)

on Friday October 13, 2006 @06:27PM (#16431793)
It's bad luck to be superstitious.

yo.

• #### paraskevidekatriaphobics - a new word (Score:2)

The article mentions that the Fear of Friday, the 13th is called Paraskevidekatriaphobia ... Google only has 1,650 results [google.com] with Urban Legends [about.com] the first one. I gotta believe a double whammy for those superstitious people to have it fall on Halloween [komar.org] - D'OH! ;-)
• #### Re:paraskevidekatriaphobics - a new word (Score:5, Funny)

<mattmacf&optonline,net> on Friday October 13, 2006 @06:40PM (#16431945) Homepage
Halloween, however, is celebrated on October 31, therefore, it's only superstitious for those crazy Europeans who insist on writing the date backwards.

; D
• #### Scheiße! (Score:2, Funny)

I always confuse Halloween and Christmas.

- Octo Weinstein
• #### Re:Scheiße! (Score:5, Interesting)

on Friday October 13, 2006 @07:44PM (#16432515) Homepage Journal
Well, of course... because Dec 25 = Oct 31

(decimal and Octal, that is)
• #### Re: (Score:2)

I'm a little unclear as to how Friday the 13th could fall on October 31st?

On another note, that urban legends article is pretty interesting; it cites a study [nih.gov] from the British Medical Journal that claims that although the number of people driving goes significantly down on a friday the 13th, the number of accidents goes significantly up. Anyone know anything about this study, or if anyone has tried to replicate these disconcerting results?

On another note, I fell down half a flight of stairs today -- sta
• #### Re: (Score:2)

I meant to say NEAR (not on) Halloween - although ironically, 31 is 13 flipped ... so just read it backwards! ;-)

Sorry 'bout the typo.

• #### A physicist? (Score:3, Insightful)

on Friday October 13, 2006 @06:27PM (#16431801)
They needed a physicist to figure out the last time that happened?? Couldnt most first year CS majors write a program to calculate this??
• #### Re: (Score:2)

No. It is just that a physicist is the only type of person taht would sit there and think "I wonder when this happened last....."

jason
• #### Re: (Score:2)

I dunno. I'm just a tech and when my daughter was born I noted that she was born on Friday the 13th on a full moon, so I wondered:
"gee I wonder how often that the 13th is a Friday and a full moon?"
Answer? 11
For whatever reason I thought that was pretty cool, so her 11th and 22nd birthdays are going to be huge, her 33rd likely se will want to ignore :-)
-nb
• #### Re:A physicist? (Score:4, Interesting)

on Friday October 13, 2006 @08:06PM (#16432669)

Here's a cute little first-year CS problem: show that with the current calendar the 13th of a month has a higher probability of falling on a friday than any other day of the week.

• #### Re: (Score:2)

They should have just found an autistic guy.
• #### European Dates (Score:5, Informative)

on Friday October 13, 2006 @06:29PM (#16431817) Homepage Journal
``The digits in the numerical notation for the date add up to 13 whether you write it in the US or the European form.''

That may be related to the fact that they are the same digits, only in a different order.

By the way, there isn't really such a thing as a "European form". Different European countries have different conventions about writing dates.
• #### Re:European Dates (Score:5, Insightful)

on Friday October 13, 2006 @06:51PM (#16432067)
• #### How about something more interesting? (Score:5, Interesting)

<sv.dude@gmail.com> on Friday October 13, 2006 @06:37PM (#16431909) Homepage Journal
Like it's the anniversary of the supposed origin of Friday the 13th being unlucky? October 13, 1307 [wikipedia.org]
• #### Every number/date/etc. is unique somehow (Score:2, Insightful)

If you find one that isn't, then it's unique in being the first one that isn't.
• #### European form (Score:4, Insightful)

on Friday October 13, 2006 @06:42PM (#16431967) Homepage
What about the African form? ;)

no text
• #### self-promoting talking head? (Score:2, Interesting)

"But it's not exactly TGIF [washingtontimes.com] for the 21 million Americans who fear the day. Some may not travel or even get out of bed, said Donald Dossey, a North Carolina psychologist who coined the term "paraskevidekatriaphobia" 20 years ago. He estimates that the nation is out \$900 million in lost productivity because of Friday the 13th sick-outs."

How do they come up lost productivity statistics anyway?

• #### Um.. not so phenomenal? (Score:5, Informative)

by Anonymous Coward on Friday October 13, 2006 @06:51PM (#16432073)
Hasn't anyone noticed by now that this year, there was a Friday the 13th in January, which has the exact same digits as today? (01/13/2006 vs 10/13/2006)
Meaning.. this phenomenon has happened within the last year?
• #### Re:Um.. not so phenomenal? (Score:5, Informative)

on Friday October 13, 2006 @06:59PM (#16432149)
Hasn't anyone noticed by now that this year, there was a Friday the 13th in January, which has the exact same digits as today? (01/13/2006 vs 10/13/2006)
Meaning.. this phenomenon has happened within the last year?

Parent is right: 01/13/2006 was a Friday. You may wanna mod the dude up.

Not that it matters either way, but this omission further proves that fatalysts and numerologists are quite slow mentally.
• #### Re: (Score:3, Insightful)

Grandparent: Hasn't anyone noticed by now that this year, there was a Friday the 13th in January, which has the exact same digits as today? (01/13/2006 vs 10/13/2006) Meaning.. this phenomenon has happened within the last year?

Parent: Parent is right: 01/13/2006 was a Friday... this omission further proves that fatalysts and numerologists are quite slow mentally.

Furthermore, 2006-1520 = 486, not 476. Quite slow indeed. It's fun to blame the universe for everything that goes wrong all day when there's

• #### Re: (Score:2)

It's fun to blame the universe for everything that goes wrong all day when there's a Friday the 13th, but people who take the whole thing seriously should be shot in the face with a bazooka.

You better do it today, while they are weak!
• #### Re:Um.. not so phenomenal? (Score:5, Funny)

on Friday October 13, 2006 @09:40PM (#16433091) Homepage Journal
But don't shoot them today! That would just convince more people that Friday the 13th is unlucky.
• #### Re: (Score:2)

They were so unlucky that they got the sums wrong!
• #### 10 + 13 + 2006 = 2029...these add up to 13 too!! (Score:5, Funny)

on Friday October 13, 2006 @06:59PM (#16432155)
10+13+2006 = 2029 2+0+2+9 = 13 aaaaaaaaaaaaaaaaaaaaaaaaaaaahhhh! all hell is breaking loose!!!!!!!
• #### Old news! (Score:5, Funny)

<robin@kalDEGASlisti.net.nz minus painter> on Friday October 13, 2006 @07:03PM (#16432181) Homepage
Slashdot is behind the times again! According to all my calendars, it's been Saturday the 14th for 13 hours already :)
• #### Re: (Score:2)

Ah you crazy kiwis, always out there on the bleeding edge ....
• #### The first Friday the 13th.. (Score:5, Informative)

on Friday October 13, 2006 @07:03PM (#16432185) Homepage
On Friday, October 13, 1307 (a date possibly linked to the origin of the Friday the 13th legend), Philip had all French Templars simultaneously arrested, charged with numerous heresies, and tortured by French authorities nominally under the Inquisition until they allegedly confessed. This action released Philip from his obligation to repay huge loans from the Templars and justified his looting of Templar treasuries. From http://en.wikipedia.org/wiki/Knights_Templar [wikipedia.org]
• #### "Pure chance," (Score:5, Funny)

<owen AT annicnova DOT force9 DOT net> on Friday October 13, 2006 @07:12PM (#16432257)
From TFA:-

'"Pure chance," the good professor told the press yesterday. '

Er right then, and there was me thinking the dates were pretty much predictable. I have a sort of flip chart thing on my wall that has successfully predicted all the dates this year - in sequence! It has pictures of cars on it too, which is nice.
• #### Re: (Score:2)

he is a physist.
Clearly he was talking about the existence of the universe that has linear time that has life that creates a calendar was pure chance.

• #### That's "31" Backwards (Score:3)

on Friday October 13, 2006 @07:27PM (#16432365) Homepage Journal
And what Friday the 13th could be creepier than one in October?

The Catholics who made our modern calendar had a wicked sense of humor.
• #### Unlucky my ass.. (Score:3, Funny)

on Friday October 13, 2006 @07:30PM (#16432397)
Unlucky my ass. I was #7 for preordering my Wii this morning....
• #### Re: (Score:2)

Ah yes, but just wait, when you finally get it, your Wii will turn out to be haunted by giant crabs from historical Japan which you can hit the weak point of for massive damage. Spooooooky.

(I was number 21 of 21 Wiis at my store. My lucky day?)
• #### Birthday today (Score:2)

Does anyone else in here have a birthday today?
• #### "Crunching" the numbers (Score:3, Informative)

on Friday October 13, 2006 @07:42PM (#16432499)
If anyone else wants to "crunch" those numbers, here's some Perl:
use Date::Calc qw( Add_Delta_Days Day_of_Week );

my \$MAX_YEAR=3000;
my @date = (1,1,1);

sub summer { \$a = 0; foreach (@_) { \$a += \$_ } \$a }

while( \$date[0] < \$MAX_YEAR ) {
@date = Add_Delta_Days( @date, 1 );
if( \$date[2] == 13
&& Day_of_Week( @date ) == 5
&& summer( split '', sprintf( "%04d-%02d-%02d", @date ) ) == 13
) {
printf( "%04d-%02d-%02d\n", @date );
}
}
I get 2006-01-13 as the most recent occurrence.
• #### Knights Templar (Score:5, Interesting)

on Friday October 13, 2006 @07:45PM (#16432523) Journal
I find it funny that people regaurd today as unlucky when it's only the Aniversary of the sacking of the Knights Templar by the King of France and the Pope hundreds of years ago!

History that still effects people after so long is cool
• #### Re: (Score:2)

You do know that all history affects us to some extent, right?

I'm not talking about the Balkans or the Middle East where what your relative did to mine seven hundred years ago is a valid reason for me killing you.
• #### I see it as lucky 7 (Score:4, Interesting)

on Friday October 13, 2006 @07:58PM (#16432621)
10-13-2006 would evaluate to 1 + 0 + (-1) + 3 + (-2) + 0 + 0 + 6 which equals lucky 7.
• #### Wasn't this on South Park The other night? (Score:3, Funny)

on Friday October 13, 2006 @08:02PM (#16432635)
Cartman: Twelve contains the numbers 1 and 2 just like the toilet yesterday where somebody went #2 instead of #1. Add 2 and 1 with 911 and you get 914. Drop the 4 and its 91. Exactly the score Kyle got on his spelling test 12 days after 9/11!
• #### Ahh, I remember it well ... (Score:2)

the time was 1:23:45 on the 6th day of the 7th month of the year '89.

How we celebrated !

Happy days, happy days ....

Of course, we all thought digital watches were a pretty neat idea.

• #### 1+2 = 3, But It's a Shock 2+1 Does Too (Score:2)

"whether you write it in the US or the European form"

So you mean those mythical and mostly unknown rugged nomads and cave people of Europe use the same calendar we do? Wow!

• #### I don't believe in Friday 13th (Score:2)

I believe in Thursday the 12th. It's the day you should stay in bed.

I was late for work
At work a laptop irrepairably failed
A co-worker got fired
More workload added
None of my scripts worked
Power went out in the building
Imaging a computer failed 3 times
Went home late, started snowing heavily on the way home
No dinner ready
Dinner tasted bad
Had to get gas
Had to pick friend up unexpectedly
Got a ticket speeding for gas and friend
Was late picking up friend
Very late for a gathering
Had to see ex-girlfriend
Seems like
• #### Re: (Score:2)

My Thursday the 12ths have always been bad as well. I only had my car towed yesterday though, so it doesn't quite compare to the day you had. :/
• #### Playing with dates (Score:3, Interesting)

on Friday October 13, 2006 @11:05PM (#16433549) Homepage Journal
I was just playing around with cal, reading the man page and found this:

\$ cal 9 1752
September 1752
Su Mo Tu We Th Fr Sa
1 2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

That's a really weird month. Appearently, the September Massacres happened on September 2nd, 1752. Don't know if there is a relationship there.

Also, I was playing with for loops, numsum, sed and such and came up with this list of years that also had Friday 13th in October and all the numbers added up to 13.

80
125
170
215
332
422
1133
1223
1340
1430
2006

I'm not sure whether this is accurate though with respect to the change from Julian to Gregorian calendars though. 2006 marks the 11th time this happened since the year 1. Interestingly, the 13th occurance of this will be in 2141, which is also the last one that will occur in the 3rd millinium. The 14th one doesn't occur until 3122 and there are only 20 of them total in the first 10,000 years. I guess they are pretty rare. My wife and I have actually found the number 13 to be lucky for us more than unlucky. But they are just numbers.
• #### Re: (Score:2)

Erm.. aren't they all adding up to eight ?
• #### Re: (Score:2)

I was just playing around with cal, reading the man page and found this:

\$ cal 9 1752
September 1752
Su Mo Tu We Th Fr Sa
1 2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

That's a really weird month. Appearently, the September Massacres happened on September 2nd, 1752. Don't know if there is a relationship there.

From the manpage of cal(1):

The Gregorian Reformation is assumed to have occurred in 1752 on the 3rd of September. By this time, most countries had recognized the reformation

• #### At the burger joint (Score:2)

I went for food at an A&W burger joint. Their cash register weren't working properly, they had to shout the order to the kitchen. That was unusual.

• #### Doh (Score:2)

It is fun and useful to celebrate weekends, annual events, birthdays etc.

But never forget that this very second hasn't ever happened and will never ever happen again (unless God decides to rerun this very moment of Universe 0.1 ;) ).

And I'm wasting it on Slashdot :p

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