I can't count

[Akane]

So in my notebook I marked day 26th, saturday, as the day I set the eggs and put that down as day 1. Which makes today day 6 and day 21 on the 15th, friday. That's not 21 days though.... If I count 21 days or 3weeks on the calendar it should come out on saturday which is the 16th. Do chickens hatch after 21 days or on the 21st day they've been in the incubator? (on average anyway since I know they don't always go exact)

 

[Three Cedars Silkies]

If you set them after noon, you would call the next day...the 27th...day 1. That would mean that day 21 is 8/17. If it was before noon, count the 26th as day one and day 21 is 8/16.

 

[Akane]

How do you get to the 17th for 21 days? If you count by hours and I set them afternoon of the 26th then the 27th would be 24hrs, 28th-48hrs or 2days, 29th-3days, 30th-4days, today is 5days, 1st-6days... 8th-13days.... 15th-20days, afternoon of the 16th makes 504hrs or 21 days exactly... So that afternoon they are due to hatch?

Only reason this is an issues is because i'm leaving on the 12th and getting back afternoon-evening of the 15th.