I think I'm counting right. The day they are set is zero, so if I set on a Friday, day 21 will be on a Friday, correct? I'm using a Brinsea Octagon 20, so I'm pretty confident in the parameters. I think my delayed hatch came from older eggs. I collecte them for 2 weeks before setting, and didn't turn as often as I should. 15 of the 17 hatched from day 20-21. 16 and 17 hatched day 22 and 23. The day 22 chick had splayed legs, but I strapped that one and it was corrected in 5 days. Day 23 pipped, but didn't hatch, and was stuck in the shell still when I got home from work that night. I helped it out (which I never do) and left it in the incubator overnight. It died 4 days later. I had 2 eggs that died in the shell with no pip, and most of my other eggs pipped further to the end of the shell than I expected. I think maybe my humidity was a touch high for the first 18 days I incubated the first 18 days at 40-42%. I'm dropping to 35-38% this go around. I have 24 cooking right now that will be due Feb. 6-7, so I will be able to compare the hatch rates with different humiditiesJust For Info for the ones that might not know----When it comes to incubating Day 1 starts 24hrs after you put them in the incubator---not the day you set them.
Are you using a still air incubator-----if so move the outer eggs to the middle every day if you are hand turning them---at least every couple days if you are using a turner till Lock-down. If about all your eggs are hatching late---increase your temp 1/2 degree for the next hatch and see how that goes.