MOD function behaving badly

I have to agree with Jo. If the function gives a result which is patently incorrect, then it is a bug.

You couldn't have 1+1=3, and then say that is not a bug because you use some special type of math to get the answer.

Edit: And to add to floating point math being used as an excuse, if Sixthsense's solution works perfectly accurately, then how can floating point math be an issue? They just need to redefine how the function is calculated to reflect a solution which accurately mimics the previous function.