dow.py

months = [0, 6, 2, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4]

def centuryOffset(c):
    if c / 100 == 21:
        return -2
    if c / 100 == 20:
        return 0
    if c / 100 == 19:
        return 1
    if c / 100 == 18:
        return 3
    if c / 100 == 17:
        return 5


def isleapyear(c):
    if (c / 4) * c == c:
        if (c / 100) * 100 == c:
            if (c / 400) * 400 == c:
                return True
            else:
                return False
        else:
            return True
    else:
        return False

def dow(m,d,yyyy):
    isleap = isleapyear(yyyy)
    coff = centuryOffset(yyyy)
    monthoff = months[int(m)]
    yy = yyyy - (yyyy / 100) * 100
    yy += yy/4
    yearcode = (yy % 7) + coff
    leapoff = -1 if isleap is True else 0
    if 0 < m < 3:
        return (yearcode + monthoff + d + leapoff) % 7
    else:
        return (yearcode + monthoff + d) % 7


firstofmonthdows = [dow(1,m,y+1900) for y in range(0, 100) for m in range(1,13)]
print(len([d for d in firstofmonthdows if d == 0]))