how many days does it take for a seed to sprout

[Nochowderforyou]

so do you mean with the light off or on. if the light is on but the seed is under the dirt, then the seed is still dark.... right?!

Well yes, it will still be dark. But what Hard-on is saying is that you require no light to sprout a seedling. Leaving the light on is pointless and you're just wasting energy and the lifetime of your lights. So leave the lights off until you see it popped through soil. No light is required for the sprouting/germinating process.