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332
To tell what day of the week
a date is on, prior to our present year.
Answer
First we must consider that each
common year, begins and ends on the
same day of the week. 1905 began
and Ended on a Sunday, 1906 begins
and Ends on a Monday.
A leap year
Ends one day later in the week than
it begins on.
The days of the week
fall backward as we go back in the
years, one for all years, and one more
for Every leap year.
Find the number
of years Elapsed since the date we
wish to find. Find also the number
of leap years, by dividing the number
of years by 4, and reducing their
number by 1, if the date is in the
last century, since 1900 was not
a leap year, and by 2 if in the
18# [eighteenth] century, since 1800 was not
a leap year.
The sum of the leap
and common years will be the
number of days of the week, by
which the day of the week has
been moved backward.
Divide this by 7
to find how many whole weeks this
gives and what remainder there is.
Now count the days
of the week backward, as many as
the remainder after dividing by 7
and you will have the day of the
week you require
For instance
On what day was the declaration of
Independence made July 4 1776
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333
July 4, 1906 is on a Wednesday
Since 1776 130 years have
passed, 32 of these would have been
leap years, but we must subtract 2
for 1800 and 1900 which leave 30 leap years.
The day of the week has
moved backward one day for each of
the 130 years, and another day for
Each of the 30 leap years, or 160 days in all
This Equals 22 weeks and
6 days, and 6 days back from Wednesday
is Thursday, which was July 4, 1776.
New Style was introduced
in England in 1752. The 3d [third] of September
was called the 14# [fourteenth].
This is the first day
of New Style and the day before was
September 2, 1752, the last day of old Style.
The rule given above will
apply to all dates later than September
1752, which day was Thursday.
For dates in the future
the same rule may be followed, except
that we must count forward in the
week instead of backward. Thus
On what day does Januy [January] 1
1920 fall. January 1, 1906 occurs on
Monday, 14 years intervene, 3 of which
are Leap Years. This Sets the day of the
week forward 17 days or 2 weens and
3 days, and 3 days from Monday is
Thursday. Januy [January] 1 1920 will be on Thursday.
Any date can be found the same.
Copied from Scientific American
Febry [February] 17, 1906
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