MIT 6.189 from the first problem set, the optional Zeller Algorithm

zeller.py

def zeller(A,B,C,D):
    if A == 1 or A == 2:
        A+=10
        C-=1
    else:
        A-=2
    W = (13*A-1) / 5
    X = C / 4
    Y = D / 4
    Z = W + X + Y + B + C - 2*D
    R = Z % 7
    if R < 0:
        R += 7
    if R == 0:
        return "Sunday"
    if R == 1:
        return "Monday"
    if R == 2:
        return "Tuesday"
    if R == 3:
        return "Wednesday"
    if R == 4:
        return "Thursday"
    if R == 5:
        return "Friday"
    if R == 6:
        return "Saturday"

A = int(raw_input("what month are we talking?   "))
B = int(raw_input("what is the day of the month?  "))
C = int(raw_input("what year? Just the last two digits  "))
D = int(raw_input("what century?  "))

print zeller(A,B,C,D)