I don't think as soon as they are hatched but it should be VERY easy to tell once they start getting their wing feathers. I never have of course, I'm just speculating based on how different the males and females look.
I posted pictures of mine at 11 days old I think and everyone one said it was too early, but at 14 days it was very obvious who was who! So I would say 2 weeks old is a good age. I could almost tell at 11 days but everyone thought it was too early so maybe you should wait till 14 days to be very sure . Just incase something changes along the way!