Timetable Anyone?

Am I the only one that continually finda sippy cups of "milk" that have turned to cottage cheese? How long does that take to happen. It seems like I have found cups that I know couldn't have been sitting for more than a day or two (fallen under a table, left in the back seat floor of the car, etc.) that have already started the transition. I know it's kinda disgusting, but I was just curious if anyone knew how long it takes for that science project to occur. I mean, cottage cheese is pretty darn expensive at the store, and if I could just make some on the floor of the back seat of our car, I might as well. ;-)