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Topic: Which day, but for 1900-2000??
Message: Posted by: Amirá (Mar 7, 2010 07:15PM)
Hi!

I wanna find a reliable method to ask the birth date and knowing which day was...

I found a few methods, but doesn't fit the criteria.

Any help? :)
Message: Posted by: Greg Arce (Mar 7, 2010 08:53PM)
Go to Lybray.com and get a memory book by Zufall. You'll have to memorize a hundred code words, but once you do that it's a breeze to do any day for a date... for over 600 years.

Greg
Message: Posted by: Scott Cram (Mar 7, 2010 11:23PM)
[url=http://www.lybrary.com/zufalls-memory-trix-p-58.html]Here's the book series to which Greg is referring.[/url]

[url=http://members.cox.net/beagenius/calendar.html]Here's my instructions on it, including an online program to quiz you on it.[/url]

[url=http://rudy.ca/doomsday.html]John Conway's Doomsday algorithm[/url] can seem simpler, especially if you [url=http://www.cs.wustl.edu/~ksl2/mathpoem.html]remember the poem about it[/url].

No matter which method you choose though, practice is the key. Worry about accuracy first, and the speed will come with practice.
Message: Posted by: TomasB (Mar 7, 2010 11:44PM)
I posted something that works nicely for dates only between 1900 and 2000 at

http://www.themagiccafe.com/forums/search_post.php?topic=110680&forum=99&post=4064377

The short formula is this, but you need to read the post to see what the variables represent:

Year 19y:

Weekday=(1+y+floor(y/4)+M+D)mod7

/Tomas
Message: Posted by: TomasB (Mar 8, 2010 02:46AM)
Sorry for the double post, but if 1900-2000 are the only dates you are going to be interested in include the 1 in the M code so the formula becomes

Weekday=(y+floor(y/4)+M+D)mod7

and the M codes for the months become

0-3-3, 6-1-4, 6-2-5, 0-3-5

/Tomas
Message: Posted by: Amirá (Mar 11, 2010 01:34PM)
Thanks !!!!
Message: Posted by: Mr. Mindbender (Mar 22, 2010 02:27AM)
Paul Brook's book "The Chrysalis of a Polymath" has a terrific version. It took me about an hour to wrap my head around it. Although it applies to any year, he focuses on 1900's & 2000's.
Message: Posted by: Scott Cram (Mar 22, 2010 11:59AM)
I agree with Mr. Mindbender, but it should be pointed out that it basically is the Doomsday method, mentioned above.
Message: Posted by: hcs (Apr 28, 2010 08:04AM)
@TomasB
This formula was invented bei Aime Paris in 1866.
The century part is more clever expressed by
H=6-2*Y div 4
then as
H=5Y+floor(Y/4).

See my Encyclopedia about calendar math "calendar in the head - the grail":
http://www.lybrary.com/kalender-kopf-gral-p-35993.html
I aplogize but this book is available only in German.
The grail includes a lot of different known and unknown methods and brand new concept of easy memorizing century-year-key number relationship.
Message: Posted by: TomasB (Apr 28, 2010 12:54PM)
Many thanks hcs! That looks a lot easier.

I'm just not sure how it works or relates to formula I wrote. The one you show gives the same H for the years starting with 16, 17, 18 and 19 while mine doesn't. Or am I misunderstanding what you mean by "div"? The way I interpret "div" is to divide by 4 and get rid of any decimals, which would make the expression constant for four centuries in a row.

/Tomas
Message: Posted by: Scott Cram (Apr 28, 2010 02:20PM)
Here's a couple of more interesting alternative calendar approaches:

[url=http://plus.maths.org/issue54/features/polsteross/index.html]On what day of the week were you born?[/url]: This one features an interesting approach using keys for decades!

[url=http://books.google.com/books?id=WSYDAAAAMBAJ&pg=PA22&lr=&as_brr=0#v=onepage&q&f=false]Abel Strook's formula[/url]: This formula uses only 2 numbers. The catch? You have to know how far into the year a given date is, such as April 15th being the 105th day of the year (which can be learned in [url=http://www.lybrary.com/magic-memory-p-465.html]Thomas Harrington's [i]Magic of Memory[/i][/url]).
Message: Posted by: hcs (May 1, 2010 02:38PM)
[quote]
On 2010-04-28 13:54, TomasB wrote:
Many thanks hcs! That looks a lot easier.

I'm just not sure how it works or relates to formula I wrote. The one you show gives the same H for the years starting with 16, 17, 18 and 19 while mine doesn't. Or am I misunderstanding what you mean by "div"? The way I interpret "div" is to divide by 4 and get rid of any decimals, which would make the expression constant for four centuries in a row.

/Tomas
[/quote]
H=6-2*Y div 4
div means the remainder of a division

Examples:
16xx; Y=16
H=6-2*16 div 4=6-0=6
17xx; Y=17
H=6-2*17 div 4=6-2*1=4
18xx; Y=18
H=6-2*18 div 4=6-2*2=2
19xx; Y=19
H=6-2*19 div 4=6-2*3=0
20xx=16xx….
Message: Posted by: hcs (May 1, 2010 03:07PM)
[quote]
On 2010-04-28 15:20, Scott Cram wrote:
Here's a couple of more interesting alternative calendar approaches:

[url=http://plus.maths.org/issue54/features/polsteross/index.html]On what day of the week were you born?[/url]: This one features an interesting approach using keys for decades!

[url=http://books.google.com/books?id=WSYDAAAAMBAJ&pg=PA22&lr=&as_brr=0#v=onepage&q&f=false]Abel Strook's formula[/url]: This formula uses only 2 numbers. The catch? You have to know how far into the year a given date is, such as April 15th being the 105th day of the year (which can be learned in [url=http://www.lybrary.com/magic-memory-p-465.html]Thomas Harrington's [i]Magic of Memory[/i][/url]).
[/quote]
Abel Strook's formula is very interesting. It is a variation of formula, published in 1909 by the russian mathematician J.I. Perelman, in the russian Journal "Priroda I Lyudi (nature and people), 1909, No. 22
cited in Butkevich/Selikson "Ewige Kalender (perpetual calendars)", Leipzig, 1987, p.91
(or in my encyclopedia "2.5. unechte Kennzahlmethoden (unreal key number methods), 2.5.2. "Tag I'm Jahr"-Methode ("day in year" method)):
W = (Y + Y int 4 + H int 4 – H + D – 1)div 7

Differences in formula caused by different key numbers for day of the week and that Perelman used.
Message: Posted by: hcs (May 1, 2010 03:20PM)
In my encyclopedia I descripe 2 ways how to determine the day of year in "1.3.1. "Tag I'm Jahr (day of the year"):
a) DY = 30(M - 1) + D + M'
M' is 0;1;-1/0;0;1/1;2;3/3;4;4; in leap years beginning with March +1)
b) Urs Oswald from Suisse
DY = M' + D = (153M – 457)int 5 + D
Message: Posted by: Greg Arce (May 1, 2010 04:30PM)
Wow, with all these equations I'm really glad I took the time to memorize Zufall's list. It's practically instantaneous once you practice it.

Good luck to all. It is quite an amazing feat once you have it down. In the times that I've been at a social gathering, and I do one one person, it becomes a tsunami of people wanted their birthdays done... and siblings and children, etc.

Greg
Message: Posted by: hcs (May 2, 2010 04:54AM)
[quote]
On 2010-05-01 17:30, Greg Arce wrote:
Wow, with all these equations I'm really glad I took the time to memorize Zufall's list. ...
[/quote]
This is correct. Zufall published a very powerfull memory system. The best system of his time. My equations above are not suitable for mental calculations.

In my encyclopadia I published a lot of different aproaches for determination of weekday (julian and gregorian) and other calendar parameters by equations (congruences), computistic, mental calculations and memory work.

This is not interesting for mentalists only but also for astronoms, historians, theologists, computer programmers and other scientist.

By the way I developed also a memory system for all years of a 400 years gregorian cycle on the state of 21th century. It is small, easier and more powerfull than Zufall's great system.
In May will be published a new revised edition of my book.
Message: Posted by: TomasB (May 2, 2010 08:36AM)
I see, hcs. The "div" confused me as it's much more common to write "mod".

So if I bake the lonely 6 into the M code I get

M=6-2-2, 5-0-3, 5-1-4, 6-2-4

Weekday = (y + floor(y/4) - 2*Ymod4 + M + D)mod7

Is there a good way to remake the "y + floor(y/4)" the same way? Anyway, the formula looks so much simpler now. Thanks!

/Tomas
Message: Posted by: stanalger (May 2, 2010 11:06AM)
[quote]
On 2010-04-28 09:04, hcs wrote:
@TomasB
This formula was invented bei Aime Paris in 1866.
The century part is more clever expressed by
H=6-2*Y div 4
then as
H=5Y+floor(Y/4).

See my Encyclopedia about calendar math "calendar in the head - the grail":
http://www.lybrary.com/kalender-kopf-gral-p-35993.html
I aplogize but this book is available only in German.
The grail includes a lot of different known and unknown methods and brand new concept of easy memorizing century-year-key number relationship.
[/quote]

Wow! That's an expensive e-book! It looks very interesting. Is it possible that the price listed is a typo?

hcs, do you know Ulrich Voigt?
Message: Posted by: hcs (May 2, 2010 01:40PM)
There is no typo. The book is designed for professionals only to preserve some secrets.
Of course I know Ulrich Voigt very close and I cite him very often in my book.
I dedicated him my book.
He wrote about my book „Ich bin von der Arbeit wirklich beeindruckt; es ist selten, dass auf scheinbar so abgegrasten Gebieten Neues herauskommt.“
(I'm realy deeply impressed by your work. It is very seldom to find new facts in such a well known field".)
Message: Posted by: hcs (May 3, 2010 04:01AM)
[quote]
On 2010-04-28 15:20, Scott Cram wrote:
Here's a couple of more interesting alternative calendar approaches:

[url=http://plus.maths.org/issue54/features/polsteross/index.html]On what day of the week were you born?[/url]: ...
[/quote]
Dear Scott, thank you for sharing this link. This australian source is new for me.

I describe such a method using decades in my book in chapter
2.5. unechte Kennzahlmethoden (unreal offset methods)
2.5.1. Jahrzehnt, Jahr I'm Jahrzehnt (decade, year in decade).

This "Five offset method" method is a variation of a method originated by the Indian I. E. DIVASLI.
It is in my opinion a little bit "more elegant" then the quoted method by Polster and Ross.
Here we go:

Y = 100H + 10Z + E
Y' = H' + Z' + E'
H = Y int 100
Z = Y100 int 10
E = Y mod 10

symbols
Y - year
H - number of hundreds
Z - number of decades
E - year in decade
Z' - offset for decade
E' - offset for year in decade

...
If Z even, then Z' = 2Z - 1
If Z odd, then Z' = 2Z - 4
If Z even and
0 lower equal E lower equal 3, then E' = E + 1
4 lower equal E lower equal 7, then E' = E + 2
8 lower equul E lower equal 9, then E' = E + 3
If Z odd and
0 lower equal E lower equal 1, then E' = E
2 lower equal E lower equal 5, then E' = E + 1
6 lower equal E lower equal 9, then E' = E + 2

Examples

1929
Z=2; E=9
Z' = (2*2 - 1) = 3 E' = (9 + 3) = 12 ==> 5

1934
Z=3; E=4
Z' = (2*3 - 4) = 2 E' = (4 + 1) = 5

1960
Z=6; E=0
Z' = (2*6 - 1) = 11 ==> 4 E = (0 + 1) = 1

1978
Z=7; E=8
Z = (2*7 - 4) = 10 ==> 3 E = (8 + 2) = 10 ==> 3


H': 6 - 4 - 2 - 0
M': 033 - 614 - 625 - 035
M': 623 - 614 - 625 - 035
W: 0 - Sunday, 1 - Monday ... 6 - Saturday

23. August 1994
D=23; M=8; Y=1994
H=19; Z=9; E=4
H'=0; M'=2
Z = (2*9 - 4) = 14 ==> 0 E = (4 + 1) = 5

W = (D + M' + H' + Z' + E') mod7 = (23 + 2 + 0 + 0 + 5)mod7
= 30/7 ==> 4 remainder 2 ==> Tuesday

19. Januar 2008
D=19; M=1; Y=2008
H=20; Z=0; E=8
H'=6; M'=0-1=6 (leap year)
Z' = (2*0 - 1) = -1 ==> 6 E' = (8 + 3) = 11 ==> 4
W = (D + M' + H' + Z' + E') mod7 = (19 + 6 + 6 + 6 + 4)mod7
= 41/7 ==> 5 remainder 6 ==> Saturday
Message: Posted by: hcs (May 3, 2010 04:28AM)
[quote]
On 2010-05-02 09:36, TomasB wrote:
I see, hcs. The "div" confused me as it's much more common to write "mod".
[/quote]
I'm very sorry. Of course mod is much more common then div.
[quote]
So if I bake the lonely 6 into the M code I get
M=6-2-2, 5-0-3, 5-1-4, 6-2-4
Weekday = (y + floor(y/4) - 2*Ymod4 + M + D)mod7
Is there a good way to remake the "y + floor(y/4)" the same way? Anyway, the formula looks so much simpler now. Thanks!
/Tomas
[/quote]
Here is a simple way invented by Lewis Caroll in 1887.
the "Method of Dozens" is very common:

y' = [y int 12 + y mod 12 + (y mod 12) int 4]mod 7.
Formula looks terrible but it is very simple.


Example
1929
y' = [29int12 + 29 mod 12 + (29 mod 12)int4] mod7
(29/12 ==> 2 remainder 5 and 5 int 4 ==> 1)
y' = (2 + 5 + 1)7 = 8 ==> 1

(„29 includes 2 dozens and remainder 5,
remainder 5 includes 1 leap year")

(There are still other simple calculation methods).
Message: Posted by: hcs (May 3, 2010 05:02AM)
[quote]
On 2010-05-01 16:07, hcs wrote:
[quote]
On 2010-04-28 15:20, Scott Cram wrote:
Here's a couple of more interesting alternative calendar approaches:

[url=http://plus.maths.org/issue54/features/polsteross/index.html]On what day of the week were you born?[/url]: This one features an interesting approach using keys for decades!

[url=http://books.google.com/books?id=WSYDAAAAMBAJ&pg=PA22&lr=&as_brr=0#v=onepage&q&f=false]Abel Stroock's formula[/url]: This formula uses only 2 numbers. The catch? You have to know how far into the year a given date is, such as April 15th being the 105th day of the year (which can be learned in [url=http://www.lybrary.com/magic-memory-p-465.html]Thomas Harrington's [i]Magic of Memory[/i][/url]).
[/quote]
Abel Strook's formula is very interesting. It is a variation of formula, published in 1909 by the russian mathematician J.I. Perelman, in the russian Journal "Priroda I Lyudi (nature and people), 1909, No. 22
cited in Butkevich/Selikson "Ewige Kalender (perpetual calendars)", Leipzig, 1987, p.91
(or in my encyclopedia "2.5. unechte Kennzahlmethoden (unreal key number methods), 2.5.2. "Tag I'm Jahr"-Methode ("day in year" method)):
W = (Y + Y int 4 + H int 4 – H + D – 1)div 7

Differences in formula caused by different key numbers for day of the week and that Perelman used.
[/quote]
As I am reading now in my own book Abel Stroock's formula was published in the same form by the Russian S. Drozdov in 1954 in "kratky astronomichesky kalendar na 1955 g. (short astronomical calendar for year 1955).
Message: Posted by: hcs (May 6, 2010 02:20PM)
I only have seen
[quote]
On 2010-05-02 09:36, TomasB wrote:
I see, hcs. The "div" confused me as it's much more common to write "mod".
[/quote]
div means "floor" or "int" not "mod".
Message: Posted by: PatBee67 (Jun 25, 2010 07:32AM)
Does anyone know how Zufall's method compares to Dominic O'Brien's method as published in "How To Develop A Perfect Memory" ?
Message: Posted by: Scott Cram (Jun 25, 2010 01:32PM)
PatBee67, The formula in both is the same, as it pretty much has to be.

The main differences are:

1) The particular mnemonic codes for letter that is used (Dominic uses 0=O, 1=A, etc., while Zufall uses the standard phonetic alphabet, 0=S, 1=T/D, etc.).

2) Zufall has you memorize the year codes as words/phrases, while Dominic has you put groups of years in their appropriate metal "rooms".

3) Zufall uses 0 for Sunday, up to 6 for Saturday. Dominic uses 1 for Sunday, up to 6 for Friday and 0 for Saturday. This last one doesn't really matter, assuming your other key numbers are adjusted appropriately.

BTW, regardless of which system you use, there's some great [url=http://x42.com/mp3/doy/]mp3 Day For Any Date training files available for free[/url]. They're available in both Day/Month/Year order and in Month/Day/Year order, and feature pauses of various lengths from 30 seconds all the way down to 3 seconds.
Message: Posted by: PatBee67 (Jun 26, 2010 05:07AM)
Thank you Scott for your clear explanation of the differences.

I do have Dominic O'Brien's e-book but did change the mnemonics for the numbers, as appears now just like Zufall, to the phonetic alphabet that I've been using since long.

Do you see any advantage to using the words/phrases for the years as opposed to learning which number (person) is situated in which particular mental room? I assume that Zufall has a method that groups those words?

Rgds,
Patrick
Message: Posted by: Scott Cram (Jun 26, 2010 11:18AM)
In Zufall's method, the years aren't really "grouped". The last 2 digits of each year (59, for example, from 1959) are linked with the year code (3 for 1959) through the use of a word ("album" translates to 593, indicating that the key for 1959 is 3).

You're basically remembering 100 words, made from the last 2 digits of the year plus the digit for the year code.
Message: Posted by: hcs (Jun 29, 2010 03:53AM)
In my book "Encyclopedia of weekday calculation" I explain a more modern solution for linking the year's digit keyword with year. I'm IMHO the first with a SIMPLE mental extension for the full 400 year cycle (chapter 8.3).

It is necessary to learn the 100 coded words for the 2 year digits only but not twice for year digits and years as Zufall explains!
http://www.lybrary.com/kalender-kopf-gral-p-35993.html
Message: Posted by: hcs (Jun 29, 2010 04:06AM)
BTW I've presented the opening show on the Mental Calculation World Cup in June 2010. Freddies Reyes Hernadez from Cuba is the new world record holder in weekday calculation with 74 calculations in one minute and 20 calculations (one century) in 13,47 sec. (see photo).

...I know Freddies personal records. they are much higher!
Message: Posted by: hcs (Jun 29, 2010 04:11AM)
Here comes of photo of Freddies and me on Mental Calculation World Cup in Magdeburg, Germany.
The "other all" winner was a young indian girl.
Message: Posted by: Scott Cram (Sep 26, 2010 02:31PM)
[url=http://www.youtube.com/watch?v=sRjf1ZR20iQ]Here's a video of Freddis Reyes Hernandez in action.[/url] Get ready to drop your jaw!
Message: Posted by: TomasB (Sep 27, 2010 02:34AM)
WOW! I didn't even have time to read most of the dates. Supernatural. I demand that he gets the million dollars from JREF.

/Tomas
Message: Posted by: stanalger (Oct 7, 2010 04:01PM)
Hernandez is fast, but he's no longer the fastest.
Jan Van Koningsveld from Germany is the new Mental Calendar World Recold Holder with 78 correct dates in one minute.
Message: Posted by: Michael Daniels (Oct 8, 2010 04:59AM)
Those learning Day for Any Date may be interested in the new improved version of my free interactive practice tool, which now includes solution times.

http://www.mindmagician.org/daydate.aspx

Mike
Message: Posted by: hcs (Oct 9, 2010 10:06AM)
[quote]
On 2010-10-07 17:01, stanalger wrote:
Hernandez is fast, but he's no longer the fastest.
Jan Van Koningsveld from Germany is the new Mental Calendar World Recold Holder with 78 correct dates in one minute.
[/quote]
Here is a photo. On the left is Jan van Konigsveld, on the right side is the German Robin Wirsing. Robin is also able to do more the one calculation per second.
Message: Posted by: hcs (Oct 27, 2010 04:48AM)
Sorry: Jan van Koningsveld and Robin Wersig!
Message: Posted by: ssakgul (Nov 5, 2010 01:05PM)
Hi everybody. I've just found this forum. I am not as fast as these men, but I found a new method for the calendar. I used the "method" word instead of formula, because it has no number or it needs no calculation such as addition, substraction, multiplication or the remainder. I am preparing a document for it, but it needs some corrections. When it will be finished, I want to publish it by a Creative Commons license.

PS. I've sent already the drafts to the mentioned Super Calendar Men.
Message: Posted by: Scott Cram (Nov 12, 2010 01:55PM)
[quote]
On 2010-10-07 17:01, stanalger wrote:
Hernandez is fast, but he's no longer the fastest.
Jan Van Koningsveld from Germany is the new Mental Calendar World Recold Holder with 78 correct dates in one minute.
[/quote]

[url=http://www.youtube.com/watch?v=9Av_i2JxJS0]Here's a video of Jan Van Koningsveld's record-breaking performance![/url]

[quote]
On 2010-11-05 14:05, ssakgul wrote:
Hi everybody. I've just found this forum. I am not as fast as these men, but I found a new method for the calendar. I used the "method" word instead of formula, because it has no number or it needs no calculation such as addition, substraction, multiplication or the remainder. I am preparing a document for it, but it needs some corrections. When it will be finished, I want to publish it by a Creative Commons license.

PS. I've sent already the drafts to the mentioned Super Calendar Men.
[/quote]

Thank you for this!

I've found this document posted over at [url=http://tech.groups.yahoo.com/group/MentalCalculation/files/]Yahoo's MentalCalculation Group's files section[/url] (listed as CCWN.7z). Once you download it and unpack it, you'll have a password-protected PDF, and instructions on how to contact the author for the password.
Message: Posted by: stanalger (Jan 26, 2011 10:22AM)
Yusnier Viera Romero has set some new records:
http://www.recordholders.org/en/records/dates.html
93 dates in 1 minute!
Message: Posted by: Santiago (Feb 27, 2011 09:21AM)
I've learned this algorithm and I think it's great. I love it because it's really easy.

It's called [url=http://rudy.ca/doomsday.html]Doomsday Algorithm[/url], and as you'll find, it gives the day of the week for any date (and you can do it in your head).

I hope this helps you :)

By the way

[quote]
On 2010-11-05 14:05, ssakgul wrote:
Hi everybody. I've just found this forum. I am not as fast as these men, but I found a new method for the calendar. I used the "method" word instead of formula, because it has no number or it needs no calculation such as addition, substraction, multiplication or the remainder. I am preparing a document for it, but it needs some corrections. When it will be finished, I want to publish it by a Creative Commons license.

PS. I've sent already the drafts to the mentioned Super Calendar Men.
[/quote]

This sounds really great! I'll be waiting :D

Welcome to the Café Ssakgul!
Message: Posted by: B. T. Lewis (Feb 27, 2011 08:20PM)
Just thought I'd share this link in case no one else had. It's the only method I know, though it sounds like there are loads

http://en.wikipedia.org/wiki/Calculating_the_day_of_the_week
Message: Posted by: Scott Cram (Mar 2, 2011 12:35AM)
The day of the week for any date tutorial I originally posted I'd programmed back in 1998.

Over the past 13 years, I've learned a trick or two about how it works, how the mind works with it, and how to improve it. As a result, I re-wrote the whole [url=http://gmmentalgym.blogspot.com/2011/03/day-of-week-for-any-date-revised.html]Day of the Week For Any Date tutorial with a completely new approach[/url]!

The basic formula I'm sure everybody here is familiar with: (Month Code + Date + Year Code) mod 7 = Day of Week Code

The big change is twofold: The whole thing is taught using the 21st century as the standard century (with codes adjusted accordingly), and the technique is taught in a way that helps you learn quickly, as well as build your confidence quickly.

[url=http://gmmentalgym.blogspot.com/2011/03/day-of-week-for-any-date-quiz-revised.html]There are more specialized quizzes[/url], too. This allows you to learn at a slower pace, while still remaining in control of your own learning pace.

Both the quiz and the tutorial allow comments, so you can let me know about any comments or criticisms there.