My way:
Put them in on a Saturday and consider Sunday day 1. Now 3 saturdays
later is day 21. This means you may have chicks as early as friday with the
stragglers finishing up by staurday night or sunday morning.
Like Tuff said a journal or even a calender on the wall is a good idea...
Hmmm. Don't open a single egg from a nonactive batch at the end of day 21?
A small hole will allow viewing of the chick. If it's alive it should still hatch. If it's
dead then this person does not have to agonize for another 3 days to find out they
have a bad hatch.
This is just my opinion...
No pips at all???
If I had nothing at the end of 21, assuming it is 21, then pop open the
air cell of one egg and see what is happening. If your temps were a little
low they may just be delayed.
Best of luck.