MEMORY SYSTEM FOR DATES IN OUR CENTURY

When you have finished this chapter you will be able to give
the correct day of the week for any date between the years 1900
to the present!
Two systems may be used, the first of which is faster and
simpler and applies to only one given year while the second
spans many years and is a little harder. These systems owe
much to Harry Lorayne, a well-known North American
memory expert.
Using the first of these systems, let us assume that we wish
to know the day for any given date in the year 1971. In order
to accomplish what may sound like a rather considerable feat,
all that is necessary is to remember (or jot down), the following
number:
377426415375
'Rubbish!' you might say, but when this system is explained
you will see that it is in fact very clear and easy to operate. The
individual digits of the 12-digit number represent the first
Sunday for each month of the year 1971. The first Sunday in
April, for example falls on the 4th day of the month, the first
Sunday in December falls on the 5th day of the month, and
so on.
Once you have remembered this number, and I recommend
that you remember it in the way that was explained in the Long
Number memory system chapter, you will rapidly be able to
calculate the day of the week for any date in the year.
It is best to explain this concept with examples, so let us
assume that your birthday fell on April 28th, and that you
wished to know what day the date represented. Taking the 4th
digit from your memory number you would realise that the
first Sunday fell on the 4th. By the process of adding sevens to
this initial Sunday date you rapidly calculate that the second
Sunday of the month fell on the nth (4 + 7 = 11); the third
Sunday of the month fell on the 18th (11 + 7 = 18) and that
the last Sunday of the month fell on the 25th. Knowing this
you recite the remaining dates and the days of the week until
you arrive at the date in question: April 26th = Monday;
April 27th = Tuesday; April 28th = Wednesday. In other
words your birthday falls on a Wednesday in the year 1971!
Suppose you wish to know the final day of the year. The
process is similar. Knowing that the 1st Sunday of the last
month falls on the 5th day you add the three sevens represent-
ing the following Sundays to arrive at Sunday 26th. Reciting
the next few dates and days we get: 27th Monday; 28th
Tuesday; 29th Wednesday; 30th Thursday; 31st (the last day
of the year!) a Friday.
As you can see this system can be applied to any year for
which you may especially need to know days for dates. All you
have to do is to make up a memory number for the first Sunday,
or for that matter the first Monday, Tuesday, etc. of each
month of the year, add sevens where appropriate to bring you
near to the day in question, and recite to that day.
An interesting and quick way to make use of the memory
number of one year with relation to surrounding years is to
realise that with each year the first date for-the days at the
beginning of the month goes down one, with the exception of
leap years when the extra day produces a jump of two for the
following year. In the years 1969, 1970, 1971 for instance the
first Sunday for January in each of those years fell respectively
on the 5th, 4th, and 3rd days of the month.
The second of the two systems to be introduced in this
chapter is for calculating the day for any date from 1900 to the
present. It is necessary in this system to ascribe to each month
a number which will always remain the same. The numbers
for 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 in
February is r which represents 4, and so on but I think that it
is better to use the number:
144025036146
making the words drawer, snail, smash and tired. These can
then be linked by imagining a drawer on which a snail with a
very hard shell is eventually smashed after an effort which
made you tired. In this way the key numbers for the months
can be remembered.
In addition to the key numbers for the months the years
themselves have key numbers and I have listed them from
1900 to 1984, after which date, according to George Orwell,
memory will be 'taken care of!'.
2
I
6
0
3 5
4
1902 1903
1901
1905
1900
1904
1909
1913
1908
1907 1911
1906
1910
1915
1919
1914
1916
1912
1917
1921
1920
1924
1925
1922
1918
1923
1927
1926
1930
1931
1929
1928
1933
1932
1937
I94I
1936
1934
1939
1935
1938
1943
1942
1940
1945
1944
1947
1949
1948
1946
1952
1950
1951
1953
1955
1954
1961
1958
1956
1959
1957
1965 i960
1967
I969
1962
1964
1971
1963 1966
1972
1970
1973 1982
1977
1968
1975
1978
I98O
1976
1979 1983
1974
1981
1984
How does this system work? Well, for once the answer is
that it is not completely easy although with a little practice it
can become almost second nature. The method is as follows,
given the month, numerical date, and the year, you add the
number represented by the month key to the number of the
date, and add this total to the key number representing the
year 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 of
examples, one from a recent year, and one which if you have
bought this book before the end of 1972, will be a day in the
future.
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 the
date in question which is 19, 19 + 4 = 23. To this total we
must add the key number for the year 1969. Referring to the
list we find that this is 2. Adding 2 to our previous total we
arrive at 23 + 2 = 25. Subtracting all the sevens from this
(3 X 7 — 21) we arrive at 25 — 21 = 4. The day in question
is consequently the 4th day of the week which is a Wednesday!
The date in the future we shall be concerned with is August
23rd 1972. Our key number for August is 3 which we add to
23 giving 26. The key number for the year 1972 is 6 which
added to 26 gives us a total of 32. Subtracting all the sevens
(4x7 = 28) from 32 we arrive at 4. The 4th day of the week
is a Wednesday which is the day for August 23rd, 1972!
The only exception to this rule occurs in leap years, and
then only in the months of January and February. Your cal-
culations will be identical but for these two months only the
day of the week will be one day earlier than the day you cal-
culate.
As with other systems the best way to gain confidence with
those discussed in this chapter is to practise them. I suggest
that you start with the easier of the two first, become skilled
in it, and then graduate to the more advanced. Both of these
systems are excellent for entertaining your friends and social
acquaintances.