Slightly high or low temperature during incubation can cause early or late hatches. I've heard of 23 - 25 days.
I will also admit I once set 18 eggs and only had 7 at lockdown and got 0. The only choice I had was to try again!
Don't get discouraged! There are a ton of variables!
First 12 in lockdown. 4 Swedish flower and 8 barnyard mutts. This run was to check out equipment for the big hatch starting next week. If the mutts hatch, I guess I can use them as layers.
Chicken person - hoping you see or hear something when you get home!
Everyone else - glad you're getting babies already!