How long can a egg sit before you incubate it?

I found an egg (Duck egg) in my landscaping, I saw a few ducks hanging around but they are no where to be seen. I waited several hour and no return. I brought the egg in the house and put a light on it to keep itwarm, I do not think I have it warm enough, So it has been 12 hours at least since it was laid, can I still plan on hatching it if I give it the correct condition as the internet describes?