Ok, you've germinate your seed, so when do you put them within direct sunlight?
Answers: I would start very slow, about 30 minutes respectively day for the first 3 days and then budge to about to about hour subsequent couple days and keep increasing some each morning. Getting to much sun the first week they will wilt and die.
good Luck
Anytime. And if you aren't using grow lights the sooner the better. Just don't leave them near for very long at a time the first few days. In nature most adjectives plants see direct sunlight the moment they break the soil surface or even before. When we germinate them indoors and they haven't seen the sun they necessitate to "hardened" a bit at a time, much the same as if you were to start working on a suntan. An hour within the early morning sun at first, working up to a full day within a week or so usually will do it. Keep a close eye on them and move them into shade if they start to wilt even a bit. You will develop a feel for what they like.