how many days does it take for a seed to sprout

[HARDDON]

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?!

Yes the seed is in the dark...

So why have the light on at all?

The light will only serve to dry the top layers of soil out and you dont want that.

Keep it moist and dark.