MEMORY SYSTEM FOR DATES IN OUR CENTURY

When you have finished this chapter you will be able to givethe correct day ofthe week for any date between the years 1900to the present!Two systems may be used, the first of which is faster andsimpler and applies to only one given year while the secondspans many years and is a little harder. These systems owemuch to Harry Lorayne, a well-known North Americanmemory expert.Using the first of these systems, let us assume that we wishto know the day for any given date in the year 1971. In orderto accomplish what may sound like a rather considerable feat,all that is necessary is to remember (or jot down), the followingnumber:377426415375'Rubbish!' you might say, but when this system is explainedyou will see that it is in fact very clear and easy to operate. Theindividual digits of the 12-digit number represent the firstSunday for each month of the year 1971. The first Sunday inApril, for example falls on the 4th day of the month, the firstSunday in December falls on the 5th day of the month, andso on.Once you have remembered this number, and I recommendthat you remember it in the way that was explained in the LongNumber memory system chapter, you will rapidly be able tocalculate the day of the week for any date in the year.It is best to explain this concept with examples, so let usassume that your birthday fell on April 28th, and that youwished to know what day the date represented. Taking the 4thdigit from your memory number you would realise that thefirst Sunday fell on the 4th. By the process ofadding sevens tothis initial Sunday date you rapidly calculate that the secondSunday of the month fell on the nth (4 + 7 = 11); the thirdSunday of the month fell on the 18th (11 + 7 = 18) and thatthe last Sunday of the month fell on the 25th. Knowing thisyou recite the remaining dates and the days of the week untilyou arrive at the date in question: April 26th = Monday;April 27th = Tuesday; April 28th = Wednesday. In otherwords your birthday falls on a Wednesday in the year 1971!Suppose you wish to know the final day of the year. Theprocess is similar. Knowing that the 1st Sunday of the lastmonth falls on the 5th day you add the three sevens represent-ing the following Sundays to arrive at Sunday 26th. Recitingthe next few dates and days we get: 27th Monday; 28thTuesday; 29th Wednesday; 30th Thursday; 31st (the last dayof the year!) a Friday.As you can see this system can be applied to any year forwhich you may especially need to know days for dates. All youhave to do is to make up a memory number for the first Sunday,or for that matter the first Monday, Tuesday, etc. of eachmonth of the year, add sevens where appropriate to bring younear to the day in question, and recite to that day.An interesting and quick way to make use of the memorynumber of one year with relation to surrounding years is torealise that with each year the first date for-the days at thebeginning of the month goes down one, with the exception ofleap years when the extra day produces a jump of two for thefollowing year. In the years 1969, 1970, 1971 for instance thefirst Sunday for January in each ofthose years fell respectivelyon the 5th, 4th, and 3rd days of the month.The second of the two systems to be introduced in thischapter is for calculating the day for any date from 1900 to thepresent. It is necessary in this system to ascribe to each montha number which will always remain the same. The numbersfor the months are as follows:
January— 1
February— 4
March— 4
April— 0
May— 2
June— 5
July— 0
August— 3
September — 6
October— 1
November — 4
December — 6
Some people suggest that these be remembered using asso-ciations such as January is the first month, the fourth letter inFebruary is r which represents 4, and so on but I think that itis better to use the number:144025036146making the words drawer, snail, smash and tired. These canthen be linked by imagining a drawer on which a snail with avery hard shell is eventually smashed after an effort whichmade you tired. In this way the key numbers for the monthscan be remembered.In addition to the key numbers for the months the yearsthemselves have key numbers and I have listed them from1900 to 1984, after which date, according to George Orwell,memory will be 'taken care of!'.
0
1900
1906
1917
1923
1928
1934
1945
1951
1956
1962
1973
1979
1984

I
1901
1907
1912
1918
1929
1935
1940
1946
1957
1963
1968
1974

2
1902
1913
1919
1924
1930
I94I
1947
1952
1958
I969
1975
I98O

3
1903
1908
1914
1925
1931
1936
1942
1953
1959
1964
1970
1976
1981

4
1909
1915
1920
1926
1937
1943
1948
1954
1965
1971
1982
5190
4191

0
1921
1927
1932
1938
1949
1955
i960
1966
1977
1983

6
1905
1911
1916
1922
1933
1939
1944
1950
1961
1967
1972
1978

How does this system work? Well, for once the answer isthat it is not completely easy although with a little practice itcan become almost second nature. The method is as follows,given the month, numerical date, and the year, you add thenumber represented by the month key to the number of thedate, and add this total to the key number representing theyear in question. From the total you subtract all the sevens,and the remaining number represents the day in the week,taking Sunday as day i.In order to check this system, we will take a couple ofexamples, one from a recent year, and one which if you havebought this book before the end of 1972, will be a day in thefuture.The day we will try to hunt down is the 19th March, 1969.Our key number for March is 4 which we must then add to thedate in question which is 19, 19 + 4 = 23. To this total wemust add the key number for the year 1969. Referring to thelist we find that this is 2. Adding 2 to our previous total wearrive at 23 + 2 = 25. Subtracting all the sevens from this(3 X 7 — 21) we arrive at 25 — 21 = 4. The day in questionis consequently the 4th day ofthe week which is a Wednesday!The date in the future we shall be concerned with is August23rd 1972. Our key number for August is 3 which we add to23 giving 26. The key number for the year 1972 is 6 whichadded to 26 gives us a total of 32. Subtracting all the sevens( 4 x 7 = 28) from 32 we arrive at 4. The 4th day of the weekis a Wednesday which is the day for August 23rd, 1972!The only exception to this rule occurs in leap years, andthen only in the months of January and February. Your cal-culations will be identical but for these two months only theday of the week will be one day earlier than the day you cal-culate.As with other systems the best way to gain confidence withthose discussed in this chapter is to practise them. I suggestthat you start with the easier of the two first, become skilledin it, and then graduate to the more advanced. Both of thesesystems are excellent for entertaining your friends and socialacquaintances.