Re: "two time periods with only an endpoint in common do not overlap" ???

[Rob Sargent]

I was afraid you were going to say that.  It's completely bizarre, but 
seems to be a "thing" in computer science.

Or maybe it's a "math thing".  But an overlap implies some length. A 
point has no length.  Maybe think of them as abutting one another? One 
ends /there/, the other starts /there/.