Question
I am in zone 7b.  What is the time frame for planting, aerating, fertilizing a new lawn with tall fescue and bluegrass seed?  When is the latest it should be done?

Answer
Early to late september is the preferred window. Much later than that and the lawn will not establish properly. If you have a warm fall, you can probably strech it to first week of October, but I would not go much longer.

You can fertilize later. In fact, it is best to fertilize a lawn in september and then again after frost has occurred and the lawn no longer grows (but before a heavy freeze has stopped the lawn). In your area, mid september and mid/end november will be good times to fertilize. Especially the last application gives good build up of energy in the crown, roots and rhizmes of the grass plants.

Aerating is best done in september.