If the 8 1/2 months ends on a Saturday (in this case 9/15/07), doesn't the client's check have to be dated 9/15 and if he dates his check 9/17, he's OK for deduction purposes but not minimum funding?

I often wondered what constitutes a half month. If a Plan Year ends January 31, is 8 1/2 months October 15 or October 16.

I suspect your question may be addressed in some early EA meeting "Grey Book."

Yes, it has been. The IRS has a code section that allows for some things to be automatically extended if the deadline falls on a weekend or holiday. The IRS takes the position that the aforementioned code section does not apply to minimum funding. I don't agree with them, but heck, forewarned is forearmed, right?