‘NAMING THE DAY’ 171

This number is then divided by 7 and the remainder from
this division indicates the position of the day in the week. If
there is no remainder, the required date is a Sunday.
97-+%7=13 (remainder 6)

and the required date therefore falls on the sixth day after
Sunday; that is, on a Saturday.

For the century 1800-1899, the procedure is the same but
the monthly code numbers are different. They are, in order:

BT AR Gy 0 i D
Thus for the date 25th December 1854, we have:

(@) 54
(b) 13
(¢) o
(d) 25
92--7=13 (remainder 1)
so that this date fell on a Monday.

In point of fact, however, there is no need to memorize
the different monthly code numbers for the century 1800
1899. Ifit is desired to find the day on which any date fell in
that century, this may be found just as easily by working out
the same date in the twentieth century and adding 2 to the
total. The total for the date 25.12.1954 was 97. Adding 2
to, this total gives 99. The division of the latter number by 7
leaves a remainder of 1, which is the same as the remainder
resulting from the division of the total (92) for the date
25.12.1854.

It is not known who first discovered this formula. It is men-
tioned in Walsh’s Handbook of Literary Curiosities, published in
1892 (though the monthly code numbers quoted there are
incorrect), but-its origin is probably much older.

Another interesting fact is that in any year other than a
leap year, the first and last days of the year fall on the same
week-day in their respective weeks. This is because the last
day is 364 days later than the first day, and the number 364
is exactly divisible by 7.

1
2
B
2
£
=
H
2
§
$
§
£
:
H