The Silverwing trilogy includes the books Silverwing, Sunwing, and Firewing. Darkwing is a prequill to the books, and is in the Cretaceous Period.
Silverwing, Sunwing, and Firewing were set in somewhere between 1942 and 1945, since the bats were shown being used as bombs near Carlsbad, New Mexico on May 15, 1943. The average lifespan for bats is 20-30 years, and Shade when this happened, was about a year and a half old. The amount of time that the three first books went through was about 3 years, but this is not proven and is an educated guess.