Best time to overseed

I'm assuming fall but thought I'd ask to confirm. The field was seeded last spring and turned out decent, but could be better. I'll overseed with a basic mix nothing special. Any advice or resource would be great. We had a neighbor help seed originally but this time I'm thinking of using my lawn mower and pull behind grass seed spreader. It'll take a while but I only have 8 acres.

Best time to overseed