Technical question about counting hatching days, I may have my due date off

[MA Mama]

How does the counting of days work? When we say they "hatch on day 21", does that mean that they hatch in the 21st day (leading up to 21 days completed), or when 21 days have been completed (in the day leading up to 22 days completed). Like "Day 1" is counted as UP TO one day complete OR the day following 1 day completed? For instance, we call a child has completed one year of life "1", not a child in the first year of it's life. I hope I am explaining myself right here. And i do realize that chicks can hatch early or late, but I am looking for the optimum hatch date if all goes right.

On Thursday night my chicks will have completed 21 full days of incubation. Last night (completed 19 days of incubation) they were all rocking and one piped. I assumed that they weren't due until Friday (Thursday night marks 21 days COMPLETED). Was I wrong? When would they be due?

 

[hdowden]

this might help

ok if you set in the am such as 9 am the nesxt day at 9 am would complete day but you would count the day you set the egg as day 1 ex.

fri @ 9am = day 1
sat @ 9 am = day 2
sun @ 9 am = day 3

if set in the pm hours the following day would be day 1 ex

fri @ 3 pm = day 0
sat @ 3pm = day1
sun @ 3 pm = day2

eggs may hatch on day 19 - 24 depending on the temp at which they were incubated if temp is a little low then they would hatch a little late if temp was a little high they may hatch early if temp was just right then they should hatch on the 21st day.

what day and time did you set the eggs? my guess would be fri the 20th or sat the 21?

 

[MA Mama]

I set the eggs January 19th at night. I think you have answered my question, and they are due 1 day earlier than I thought! THANKS!

 

[hdowden]

yes they are ready to hatch a day early (day 20)

happy hatching