Page 204 - Use Your Memory

16 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 and
2000!
Two systems may be used, the first of which is faster and
simpler and applies to only one given year, whereas the second
spans 100 years and is a little more difficult. These systems owe
much to Harry Lorayne, a well-known North American memory
expert. Using the first of these systems, assume that you 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 the following number:
377426415375
'Impossible!' you might say, but once 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 fourth day of the month, the first Sunday in
December falls on the fifth day of the month, and so on. Once you
have remembered this number (if you have difficulty, refer back to
the chapter on Long Number Memory) 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 28 April, and that you wished to know what
day the date represented. Taking the fourth digit from your
Memory Number you would see 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
1lth (4 + 7 = 11); the third Sunday of the month fell on the 18th
and the fourth Sunday 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: 26 April = Monday; 27 April = Tuesday; 28 April =
Wednesday. So your birthday fell on a Wednesday in 1971.
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