how long can eggs be in a nest and still be good to eat?

[kwhitlow]

i brought three laying wyandotte hens home about two weeks ago. the first day one of them laid an egg. then nothing untill yesterday when i found a dozen eggs in the monkey grass. i knew that by letting them roam the back yard they might find their own place to go but i some how didn't see these. how long can the eggs be outside and still be safe to eat ?