On Day 2, Jesse says Andy's leaving "tomorrow", which was marked as the first Friday of September. This places the movie as happening from September 1 to September 3, and since the August calendar was drawn on a whiteboard it may just be early in the day, before Andy had a chance to change it to September (there's also a digital calendar in Sunnyside, but it doesn't line up with the days correctly anyway so I'm disregarding it's August reading).
I'm pretty confident with all these Toy Story placements, though I'm not so sure on the credit clips, I believe they just take place shortly after, though it would be nigh impossible to get exact dates for it.
I can't believe I'm going to be unironically watching Toy Story Toons now…