I would imagine this fall.
I did the same thing and I seeded 2 weeks later and turned out great!
Unless Scotts is selling some crabgrass preventer I have not seen then the PREVENTER is going to PREVENT your grass seed from germinating and coming up. Now that does not mean you cannot try it. But as a general rule unless special preventers are used then you must wait for several months to seed grass after using something like Halts from Scotts. If you did not put on a preventer, just fertilizer or fertilizer plus post emergeant broadleaf weed killer then you can seed much sooner. It is getting to late to plant grass around here anyways. Perhaps where you are will be ok. The best looking lawns as a rule come from sod. The best seeded lawns at least in the midwest come from seed planted in late summer early fall. I planted some grass this spring. it looks pretty good. But I doubt it will survive the summer heat in the shade.
Look up lawn calendar Cornell University. Lots of good information on time and season for seeding, mowing , fertilizer etc. Any university I have looked at have a lawn care program. Some are better than others but all have good information on lawncare. You tube has some pretty good stuff if you look some, so does some big box stores. You need to get started right. Or its going to be uphill all the way.