Every used variable are integer type
- If Month = 1 or Month = 2 then,
- Month = Month+12
- Year = Year-1
- Weekday = ( Day + 2*Month + (6*(Month+1)) div 10 + Year + Year div 4 - Year div 100 + Year div 400 ) mod 7
Equivalence between the weekday and the day name
- Weekday = day name
- 0 = Monday
- 1 = Tuesday
- 2 = Wednesday
- 3 = Thursday
- 4 = Friday
- 5 = Saturday
- 6 = Sunday
Particularity : Every year, the 4/4 (April 4th), the 6/6 (June 6th), the 8/8 (August 8th), the 10/10 (October 10th) and the 12/12 (December 12th) come the same weekday.