Do you count the first day of incubation?

How do I count the days? Count the days of incubation from the first day the eggs are placed in the incubator. If placed in the a.m. that day would be Day 1; if placed in the p.m. that day would be Day 0, the next day would be Day 1.

How do you know if eggs are fertile before incubation?

If the egg is fertile, then you should see a dark spot around the middle of the egg, with some spider-like veins beginning to form around it. If its not, you should just be able to see the shape of the yellow yolk inside the egg, without any signs of an embryo or veins.