This Rare Friday the 13th

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."

Comments

I Just Knew I Shoulda Stayed In Bed Today

[ackthpt]

While the sum of 2+6+1+1+3=13 is mildly interesting, I never thought much about Friday the Thirteenth outside of Pogo strips. Walt kelly's character in the strip, Churchy LaFemme 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 too.

Re:I Just Knew I Shoulda Stayed In Bed Today

[yo_tuco]

I wonder if Heinrich Hemme's calculations take into account the 10 missing days in the Gregorian calander between 4 October and 15 October 1582?

Re:I Just Knew I Shoulda Stayed In Bed Today

[enjerth]

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

[Iron Condor]

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:I Just Knew I Shoulda Stayed In Bed Today

[attonitus]

I think that the point of the GP is that it changes when the Fridays are.

Re:I Just Knew I Shoulda Stayed In Bed Today

[enjerth]

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:I Just Knew I Shoulda Stayed In Bed Today

[AstrumPreliator]

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:I Just Knew I Shoulda Stayed In Bed Today

[ari_j]

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 double leap day in 1712 to get back on Julian and then finally managed to convert to Gregorian by 1753.

Commutivity

[P(0)(!P(k) P(k 1))]

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 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?

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:Commutivity

[ackthpt]

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

[fuzzix]

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? :)

Re:Commutivity

[UglyTool]

*sigh*

1520 + 476 = 1996...

Re:Commutivity

[nebaz]

I can imagine what someone would say about the parent being 'Informative' during metamoderation. :-)

Hmm... a post showing the sum of two numbers.

Re:Commutivity

[Filthysock]

1582, never forget.

Of course, you care about that only if

[Rosco P. Coltrane]

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...

Re:Of course, you care about that only if

[Iron Condor]

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

Wow.

What country do you live in?

Can I come?

13th Post!

[markana]

sorry....

Re:13th Post!

[rolfwind]

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.

Pffft....

[yo303]

It's bad luck to be superstitious.

yo.

A physicist?

[nickmue]

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:A physicist?

[Iron Condor]

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.

European Dates

[RAMMS EIN]

``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

[orangepeel]

"Give me ISO 8601 or give me death!"

Re:European Dates

[isorox]

US notation is standardized MM/DD/YY

Which is just plain dumb. yy(yy)/mm/dd -- most significant first, is the best choice, but otherwise dd/mm/yy (least signficant first) is the next option. mm/dd/yy makes as much sence as yy/dd/mm, it's a random order.

Mod Parent Down

[s-gen]

Just to prove to him its not his lucky day.

How about something more interesting?

[winkydink]

Like it's the anniversary of the supposed origin of Friday the 13th being unlucky? October 13, 1307

Every number/date/etc. is unique somehow

[burndive]

If you find one that isn't, then it's unique in being the first one that isn't.

Re:paraskevidekatriaphobics - a new word

[mattmacf]

Halloween, however, is celebrated on October 31, therefore, it's only superstitious for those crazy Europeans who insist on writing the date backwards.

; D

European form

[JHromadka]

What about the African form? ;)

self-promoting talking head?

[vague_ascetic]

"But it's not exactly TGIF 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?

[Anonymous Coward]

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?

[suv4x4]

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:Um.. not so phenomenal?

[howlingfrog]

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 a Friday the 13th, but people who take the whole thing seriously should be shot in the face with a bazooka.

Re:Um.. not so phenomenal?

[Samurai Cat!]

But it won't happen again until January 2024.

Ehhh! Wrong.

05/13/2011. :D

Re:Um.. not so phenomenal?

[telbij]

March 13, 2004 was a Saturday.

Re:Um.. not so phenomenal?

[bcat24]

But don't shoot them today! That would just convince more people that Friday the 13th is unlucky.

aahh..but

[geekoid]

if it affects how other people behave, then it affects you.

10 + 13 + 2006 = 2029...these add up to 13 too!!

[Cobraman]

10+13+2006 = 2029 2+0+2+9 = 13 aaaaaaaaaaaaaaaaaaaaaaaaaaaahhhh! all hell is breaking loose!!!!!!!

Scheiße!

[suso]

I always confuse Halloween and Christmas.

- Octo Weinstein

Re:Scheiße!

[Kredal]

Well, of course... because Dec 25 = Oct 31

(decimal and Octal, that is)

Old news!

[Eythian]

Slashdot is behind the times again! According to all my calendars, it's been Saturday the 14th for 13 hours already :)

The first Friday the 13th..

[the_rajah]

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

"Pure chance,"

[Scooter]

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.

That's "31" Backwards

[Doc Ruby]

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..

[MioTheGreat]

Unlucky my ass. I was #7 for preordering my Wii this morning....

"Crunching" the numbers

[thisisjoel]

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

[Danathar]

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:But isn't that really 4?

[masterzora]

Good thing Japanese culture associates 4 with Death. We can maintain this silliness now!

I see it as lucky 7

[10e6Steve]

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?

[SrLnclt]

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!

Playing with dates

[suso]

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:Good form.

[TCM]

the US form makes more sense.

No it doesn't. It mixes the significance of the numbers. Your explanation hardly makes any sense because any benefit is outweighed by non-intuitiveness. You say one already knows what year it is. Well, why don't you already know the month, too? According to your "logic", the day should be the first, since it's the item that changes most frequently. Being accustomed to something != making sense.

YYYY-MM-DD is easily sortable for computers and is also the standard set by ISO 8601. This is the only correct and intuitive notation. Some countries use(d) DD.MM.(YY)YY which is at least easy to read for humans and maintains the order of most frequently changing to least frequently changing item. MM/DD/YY is just a mess and I can't count the times I've been confused by it.

All this gets worse when people use YY/MM/DD, DD/MM/YY or YYYY-DD-MM as I've seen recently, although the latter must have been a typo. As if ../../.. wasn't bad enough, they use USA syntax but ISO semantics, WTF?