... we define the third approximation of SWN as: SWN3( y, m, d ) = 1 + 4 * (m-1) + ( 2 * (m-1) + d-1 - SDOW( y, m, d ) + 5 ) / 7 By exhaustive experiments, we verified that SWN3 equals SWN for all possible values of y, m, and d. Getting rid of the division. The calculation of SWN3 still contains ...