Calendar calcualtions

[deusvult]

Hi!

I am trying to calculate difference in days between two dates. If the dates are close enough the answer is correct but as the difference increases I start getting an error.
I know there is a different way how to do it, but I would appreciate help in spotting whats wrong in this one.

print "***Calendar simulator 2.0***"
print
d1,m1,y1 = map(int,raw_input("Enter start date in DD.MM.YYYY format: ").split("."))
print
d2,m2,y2 = map(int,raw_input("Enter end date in DD.MM.YYYY format: ").split("."))
print

m111=m1-1
m222=m2-1
y11 = int((y1-1)/4.)+(y1-1)*365
if (y1)/4. == float(int((y1)/4.)):
    a = [31,29,31,30,31,30,31,31,30,31,30,31]
else:
    a = [31,28,31,30,31,30,31,31,30,31,30,31]    
m11 = sum(a[0:m111])

x = y11+m11+d1

y22 = int((y2-1)/4.)+(y2-1)*365
if (y2)/4. == float(int((y2)/4.)):
    b = [31,29,31,30,31,30,31,31,30,31,30,31]
else:
    b = [31,28,31,30,31,30,31,31,30,31,30,31]
m22 = sum(b[0:m222])

y = y22+m22+d2

diff = abs(y-x)

s = (diff % 10)
if s == 1:
    print "Difference is: ", diff, " day."
    print
    print "Ready."
else:
    print"Difference is: ", diff, " days."
    print
    print "Ready."
print x
print y