I set several posts for a deck project a while back...

One thing I also do is to make sure the bottom of the holes are flat and the dirt is least 5-6" clear around the post...

I also run a couple 8" lag bolts through the posts and then add in the concrete...

In my experience one day is not long enough to let them set up...

Sometimes the ground around them is still saturated and it moves the post and concrete around making the dirt hole larger...

The other thing that makes a big difference is the depth the poles are set into the ground...