From when the egg is laid it will be approximately 18 days until the chick hatches. Eggs are laid 2 days apart and hatch in the order they were laid. Some breeders will number the eggs so the first one is number 1, the second one is number 2 and so forth. A water based marker pen or pencil will work. Please make sure any pen you use is not oil based as this can kill the chick.