Divide the sum of these three by 7, and remainder gives the number of
the day of the week.
Thus:--What day of the week is 15th July, 1908?
1. 8 + 2 = 10
2. July = 0
3. 15th = 15
--
25 = 7 × 3 + 4
4th day of the week = Wednesday.
What day of the week was December 25th, 1905?
1. 5 + 1 = 6
2. Dec. = 6
3. 25th = 25
--
37 = 7 × 5 + 2
2nd day of the week = Monday.
The above only applies to 20th Century. For 19th Century, add 2; for
21st Century, add 6; 18th Century, 4; but before 1752 the “old style”
was used.