The calendar is good for calculations

The universal calendar ------------------------

Here is a method for determining the day of the week for a given date, using September 28, 1958 as an example. All the calculations are done "modulo 7", that is, keeping only the remainder when dividing by 7.

• Take the day of the month, here 28. We have 28 = 4 $\times \backslash times$ 7, and we keep 0.

• Take the number associated with September, namely 5 (see the corresponding table).

• Take the last two digits of the year; here, 58 = 8 $\times \backslash times$ 7 + 2 and we keep 2.