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Amirá Inner circle MentalismCenter.com 5134 Posts 
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?
Pablo
Performer and Author Mentalism Center: The best online space to get quality Mentalism www.mentalismcenter.com Arkanosophy: The Boutique for Mystery Performers www.arkanosophy.com 

Greg Arce Inner circle 6447 Posts 
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
One of my favorite quotes: "A critic is a legless man who teaches running."


Scott Cram Inner circle 2677 Posts 
Here's the book series to which Greg is referring.
Here's my instructions on it, including......u on it. John Conway's Doomsday algorithm can seem simpler, especially if you remember the poem about it. No matter which method you choose though, practice is the key. Worry about accuracy first, and the speed will come with practice. 

TomasB Inner circle Sweden 1143 Posts 
I posted something that works nicely for dates only between 1900 and 2000 at
http://www.themagiccafe.com/forums/searc......=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 

TomasB Inner circle Sweden 1143 Posts 
Sorry for the double post, but if 19002000 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 033, 614, 625, 035 /Tomas 

Amirá Inner circle MentalismCenter.com 5134 Posts 
Thanks !!!!
Pablo
Performer and Author Mentalism Center: The best online space to get quality Mentalism www.mentalismcenter.com Arkanosophy: The Boutique for Mystery Performers www.arkanosophy.com 

Mr. Mindbender Inner circle 1439 Posts 
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.


Scott Cram Inner circle 2677 Posts 
I agree with Mr. Mindbender, but it should be pointed out that it basically is the Doomsday method, mentioned above.


hcs Elite user Germany, Magdeburg 450 Posts 
@TomasB
This formula was invented bei Aime Paris in 1866. The century part is more clever expressed by H=62*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/kalenderkopfgralp35993.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 centuryyearkey number relationship.
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


TomasB Inner circle Sweden 1143 Posts 
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 

Scott Cram Inner circle 2677 Posts 
Here's a couple of more interesting alternative calendar approaches:
On what day of the week were you born?: This one features an interesting approach using keys for decades! Abel Strook's formula: 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 Thomas Harrington's Magic of Memory). 

hcs Elite user Germany, Magdeburg 450 Posts 
Quote:
On 20100428 13:54, TomasB wrote: H=62*Y div 4 div means the remainder of a division Examples: 16xx; Y=16 H=62*16 div 4=60=6 17xx; Y=17 H=62*17 div 4=62*1=4 18xx; Y=18 H=62*18 div 4=62*2=2 19xx; Y=19 H=62*19 div 4=62*3=0 20xx=16xx….
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


hcs Elite user Germany, Magdeburg 450 Posts 
Quote:
On 20100428 15:20, Scott Cram wrote: 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.
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


hcs Elite user Germany, Magdeburg 450 Posts 
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
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


Greg Arce Inner circle 6447 Posts 
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
One of my favorite quotes: "A critic is a legless man who teaches running."


hcs Elite user Germany, Magdeburg 450 Posts 
Quote:
On 20100501 17:30, Greg Arce wrote: 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.
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


TomasB Inner circle Sweden 1143 Posts 
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=622, 503, 514, 624 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 

stanalger Special user St. Louis, MO 996 Posts 
Quote:
On 20100428 09:04, hcs wrote: Wow! That's an expensive ebook! It looks very interesting. Is it possible that the price listed is a typo? hcs, do you know Ulrich Voigt? 

hcs Elite user Germany, Magdeburg 450 Posts 
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".)
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


hcs Elite user Germany, Magdeburg 450 Posts 
Quote:
On 20100428 15:20, Scott Cram wrote: 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'=01=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
Melencolia I  Magic Squares for the Mental Entertainer * Smart Methods for 4x4, 5x5 and 6x6 Magic Squares * 180 A4pages * version 3.51


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