"Perpetual" calendar card-calendar for determining the day of the week of any calendar date of the old and new style
Usage rules
In the left part of the table, find the line containing the first two digits of the year you want by the old or new style, and at the top of the table - the column with the second two digits of the year. Remember the letter at the intersection of the row and column.
In the table on the right side, find the desired month. In the line in which this month is located, find the same letter.
In the lower left part, in the "Numbers of the month" section, find the desired number. The intersection of the line in which this number is located, with the weekday column located under the letter found, gives the desired day of the week.
In this case it is necessary to distinguish between January and February in simple and leap years: they occupy different positions in the column of months: for simple years they are designated In and IIn, for leap years - Iv and IIb.
If the date before the date is found.e., First of all, the date of the historical account should be transferred to the date of the astronomical account, i.e.the number of the year is reduced by one( 143 BC = -142).Then the second two digits must be converted to a positive number, adding 100( we have -42 instead of -48), this number is searched at the top of the table.
Example 1. Determine what day will be on January 1, 1989. On the left in the column of the new style, we find the number 19, the top number is 89. At the intersection of the line and the column is the letter S. The year is not lean, so we find the same letter in the line onwhich is denoted by In. This is the same letter S. Below this letter is a column with days of the week, corresponding to January, whose numbers are on the left. So, January 1, 1989 falls on Sunday.
Example 2. Determine the days of the week that fall on the dates of M. Lermontov's life according to the old style( Z. X 1814-15 15. VII 1841).Find the number 18 on the left in the column of the old style and the numbers 14 and 41 on top. At the intersection of the line and the column in the first case is the letter T, in the second - B. From the designation of the month X, we go to the letter T( in this case it turned out to be the same), and from the notation VII - to the letter B and find: October 31814, was Saturday, and July 15, 1841 - Tuesday.