A: Because DEC 25 = OCT 31
(OK, that one is obscure. Decimal 25 is equivalent to octal 31. To check it out, you can use the windows calculator program. Click View and select Scientific. Be sure Dec is selected. Enter 25. Select Oct. You'll get 31. Jokes are pretty terrible when you have to explain them!)
And did you hear about the ghost photographer? The spirit was willing but the flash was weak.