My father owns a farm and has some chickens on it. His chickens started laying eggs about a month ago. There is only one rooster in the pen. We recently started incubating eggs and have a good temperature and humidity on the bator. However, we weren't really sure about the hatching period. According to many sites, the hatching period for chicken is 21 days. My father acctually left the eggs in open air for about 5 days before putting them in the bator. We were wondering, would it be 21 days from the day the egg was laid? Or 21 days from the day the eggs were put in the bator? Also, does anyone have any suggestions on building a strong candler? We're using dark eggs, so it's hard to see. Thanks alot.