When chicks are due on day 21......will they start hatching on..

[Hennypen]

Will they start the hatch on day 21 or will they start hatching on the 20th day and be out on the 21st day? (generally speaking of course since there seems to be variations due to temp)

Day 21 is tomorrow for me (Wed) and so far nothing has happened other than a little movement when the eggs were on their sides yesterday.

(now they're in a carton w/sides cut down)

 

[SarahFair]

Every egg is different! Some will start zipping on day 20 and be out day 21 early and some maybe not till late 21 or 22 some earlier some later