Uncategorized Tuesday, October 5th 2010 at 10:54 am

This October Has 5 Fridays, Saturdays, & Sundays, But That Happens Way More Often Than “Once Every 823 Years”

You may have heard a rumor on Twitter, by email, or wherever it is that rumors get started, that this month has 5 Fridays, Saturdays, and Sundays, and that this happens only once every 823 years. It’s not true.

Now, there are 5 Fridays — on the 1st, the 8th, the 15th, the 22nd, and the 29th; 5 Saturdays — on the 2nd, 9th, 16th, 23rd, and 30th; and 5 Sundays — on the 3rd, 10th, 17th, 24th, and 31st. You can verify that by looking at a calendar, so the “only once every 823 years” part might seem to follow by association. The first part was true, so the second has to be too, right? You’ve heard it from a lot of people, after all.

But in fact, it isn’t the case, due to the cyclical nature of the calendar. Doug Stych breaks it down:

Let’s think about this, a year can only start on one of seven days, so there are seven possible basic calendar years. Add leap years, and there are fourteen basic calendars. Period. And one of those calendars only gets used every 823 years? How would that be possible? It’s not of course, all fourteen calenders get cycled through regularly, in fact 2010 uses the exact same calendar as 1999.

Here’s the 2010 October calendar, via TimeandDate.com: (today’s date is highlighted in yellow)

And here are the calendars for October 1982, October 1993, October 1999, and October 2021. See a pattern?

To save you the trouble, 1971 and 2004 had the same October calendar, and 2032 will have the same as well. Hardly a once-every-823-years event.

(P.S. There’s a pretty simple explanation for this all: For a 31-day month to have 5 Fridays, Saturdays, and Sundays, the first day needs to be a Friday. Each nonleap year has 365 days, which is 52 weeks plus one day [52*7=364; 364+1=365.] So every passing year will ‘push’ the first day of the month forward by one day, defining ‘forward’ as Friday -> Saturday, Saturday -> Sunday, etc. However, if it’s a leap year, the first day of the month will be pushed forward by two days. Since any six-year cycle will contain at least one leap year, this means that the same October calendar should reappear every six years [five one-day pushes forward and one two-day push = one full week covered] unless there are two leap years that fall in that space, in which case the whole cycle will be shifted forward by one day.)

Update: Hah! Chris O’Leary responds to the comic that started the hoopla: (h/t TDW)

(h/t Doug’s Darkworld. title pic via Cargo Collective)

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• JN_Rut

Hello,

I think you took only half of the condition.

It was originally stated with two conditions:

# 1 10th day of the 10th month of the 10th year.

# 2 5 Fridays, 5 Saturdays and 5 Sundays.

The October months you show do not meet both conditions.

Respectfully,
JN_Rut

• BlueDog57

Check out Octobor of 2004. It also had five Sundays, five Fridays and five Saturdays.

Blue Dogs (Heelers) and Kangals rule!
Waller Texas

• Aldebaranian

JN_Rut: If you add the first requirement of 10th day of the 10th month of the 10th year then it is even more certain that it won’t happen every 823rd year! (since 10+3 is not 10…)

The next time all your criteria will take place is October 2410 and the last time was October 1210 (if you extrapolate _our_ calendar that far back…) So indeed that is rarer, but it has to occur at multiple of a century of course.

• hebe5757

This is based on the Hebrew calendar, which is why it is usually sent in Hebrew. It being based mostly on a Lunar system, this rarely happens However in the Hebrew month of Cheshvan, 5751, this DOES happen for the first time in 823 years. Hoax? I think not.
You folks need to expand your narrow range of view.

• TimothyBucks

@hebe5757 Cheshvan is normally a 29 day month and occassionally a 30 day month so for it to have three consecutive days occurring 5 times is one hell of a miracle as it requires a 31 day month.

You folks need to expand your narrow range of mathematics!!!

• biggare

@JN_RUT in the stories going around it doesn’t have your first criteria.

@aldebaranian I believe that with the criteria the last one would be 1610.

@hebe5757 Even if it had 31 days, Cheshvan 5751 starts on a Shabbat not a yom shishi.

• Lionel T Sett

The problem with trying to justify trying to use either the Jewish calendar or the Chinese calendar ( Jewish calendar and the Chinese calendar actually do synchronize quite nicely, with complementary 19 year lunar cycles, the first email I got mentioned this was a Feng shui thing,) is that in all the emails and face book postings I’ve seen always uses the term “October’ as a critical criteria. Not “the tenth month” of the year. October. I’d love to think outside the box, but the lid’s been nailed down.
There may be a calendar system that somehow could be force fit into, but I doubt it uses specific terminology like “October, Friday, Saturday, Sunday or weekend’.

Its just not good practice to try to mash measuring systems together. Or use terminology that may be obscure or unsuitable in context When asked how tall I am, I suspect the DMV wont accept “one International Fathom’ nor will they accept ‘1 meter,32 and 5/8 inches’ as answers.

• azroach

Each time it happens, it ends with Halloween. It’s pretty interesting because it is rare. I offer relocation services and this October was one of our most productive months this year!

• RinkyDinkPanther

In the past 20 years this has happened in :

January – ’93, ’99, ’10.
March – ’91, ’96, ’02.
May – ’92, ’98, ’09.
JULY – ’94, ’05.
August – ’97, ’03, ’08.
October – ’93, ’99, ’04, ’10.
December – ’95, ’00, ’06.

• Tsmith

this July has 5 fri sat sun

• Sara

So in other words this happens almost every year. what a rare phenomenon

• Owbigred

jan has 5 sat sun mon, july has 5 fri sat sun and oct 5 fri sat sun how often does a year have three months like this

• Anonymous

what?

• HollandLaw

WooooooOOOooooooOOOooooooOOO!!!

(There are 9 o’s, with six small and 3 Caps, three times over. Now THAT’s creepy!)

• Farmworkjp

this is based on the republicans calender, just like all their other e mails, lies.

• Bongani

OLD NEWS here’s the latest:
this year we are going to expirience four unusual dates:
1/1/11; 1/11/11; 11/1/11; 11/11/11 and when you take take last two digits of the year add the age you will be this year you get :111
what do you say to that!

• GeekNZ

@Bongani – I say the dates are cool, but you’ve missed a bit on the year thing – you have to be 100 for that to work!

In the version I received (your age this year plus the last two digits of the year you were born), it works for (almost) everyone, but that’s hardly surprising – adding those two numbers gives you the number of years since 1900 (assuming you were born before 2000), which is 111. If you were born in 2000 or after, they will only sum to 11.

• Sridaman

But October 2011 has 5x Saturday, 5x Sunday and 5x Monday. This may happen once in 823 years :)

• Tamiraan

for those few who were born before 1900 and still alive, it’ll be 211. someone’s taking it as a discovery. it is simple math like 2011-1900=111, 2011-2000=11, 2011-1800=211 etc. i believe everybody can do this math. all those 1111111111111111s is really rare thou. happens ONLY in every hundred years. live healthy, eat healthy u might see another 111111111111111111s.
Dang, I never knew i was good at math, anything with thinking involved.
agreed with Geek from New Zealand, i asssume. :)

• Kourounouxra

its about the year 2011! not 2010 whole article is nonsense!!

• Kourounouxra

its about the year 2011! not 2010 and its about Mondays Saturdays and Sundays!!! not fridays saturdays sundays!

• Kourounouxra

and it doesnt apply for 2011 with monday saturday sunday as we ll have the same october in 2016, 2022,..33,..39,..44,..50…

• Anonymous

• Jk

Don’t you read? There are ONLY 14 basic calendars. The very very LEAST it could happen is once every 14 years. But with leap years, it follows a 5,6,5,11 year cycle

• Amy_19

i think it was sarcasm…

• Its1110

Ummm…. It _Didn’t_ say “Cheshvan”… It said “October”.
Therefore we’ve no reason to “expand our narrow range” as the Hebrew calendar was not specified — hence, any reasonable person would use the current common civil calendar.

But, thank you for the very interesting information you provided, of which I was not aware.

A day when you do not learn something new has been a wasted day.

• Its1110

Thank You!!!!
My point exactly; stated much the better!

• Its1110

Ha ha… “Fun with Math” (C)(TM)(SM)(BS)…

By the way: Right now the soul of my left foot itches…. it doesn’t doe that very often. So _THERE’S” another_  unusual thing!

[No. I didn't mis-spell sole. (?!) Who says my feet don't have a soul? Are you sure I was talking about an anatomical part and not describing a particular 12 inch long portion of some (other) part of my body? i.e. thigh, torso
My point is... semantics, word selection, etc. are mailable things... Try hard enough and you can make anything imply whatever you wish.]

• Its1110

Hmmm…
Yes, all the ones are interesting and unique (sort of), but the _fact_ itself has always been true, since the establishment of the current civil calendar, that such would be the case.
It’s just a bunch of “observations”… to use the formal mathematical/logical term… rather than some astounding “proof” of anything.

• Its1110

Laughing at myself here…
Yeah.. I really needed _another_ way (besides Facebook) to waste 15 minutes of my life…
:)

• joji

but not only octobers have this thing. I noticed some other months ir previous years :) do not remember which ones exactly :)

• lexingtoncarguy

Is it possible that it only happens specifically in the month of JULY… every 823 years? Everyone seems to keep referencing October and/or other months….

• HarryBalszak

Nope. It happened with July in 2005 and will again in 2016, 2022, and 2033 following the 6-5-6-11 pattern mentioned above (at least until the end of this century when the pattern shifts slightly due to 2100 not being a leap year.)

• Ezzy

I need 6 sundays in a month!

• autoguy

Correct me if I am misstaken but hebrew calanders only have 29 or 30 days in them making it impossible to have this situation.

• Dheeraj

March 2013 has  5x Saturday, 5x Sunday and 5x Monday.
August 2014 has 5x Saturday, 5x Sunday and 5x Monday.

• Bioscot99

There is no Jewish calendar month that has 31 days….DUH

• Steuerjim

NOOOO……mathematically it does not!!…..check Dec 2012!!

• Steuerjim

You might want to repost……cuz 11 plus me being 39 this year makes it 50!! its take the last 2 digits of the year u were born and the age u will be this year!!!

just read a calendar from past years

• Jlieber

It is true that October 2010 has 5 Fridays, 5 Saturdays and 5 Sundays. However, there is nothing particularly “interesting” or unusual about this fact. And it is certainly not true that such a combination only happens every 823 years. In fact, such combinations occur every few years. As the following calendar shows, the next year that has a month of October with 5 Fridays, 5 Saturdays and 5 Sundays will be 2021. This is a mere eleven years in the future, not 823 years as suggested in the message:

• Gremlin984

ummm. … RE: #2: the calendars are right there: they each have 5 sat sun and fri’s
not to be totally party pooper… what about the ’20′ before the 10 in the tenth year?

Well: in any case: it is all very fun to see and am looking forward to my money bag in 4 days!!! cuz it’s happening in 2011 for NOVEMBER!! (… didn’t this happen sometime last June or July also?)
that’s okay!! it’s still fun. there’s a math thing that goes with the 11 that is even MORE fun!
(copied from someone else, it works on anyone born before the year 2000, but anyone born the year 2000 or after that will end up with 11!)

Take the last two digits of the year you were born and
the age you will be this year and the result will add up to 111 for
everyone!!!!

• Gremlin984

i meant October…  “it’s happening in 2011 for NOVEMBER!! (“

• Cmac

So does April 2012!!