The official filming dates for TWD season 8 are scheduled from 5/1- 11/16 according to this list of current projects SF is working on.

From page 13:

Walking Dead, The 08 2017 Stalwart Films, LLC
Type: Dramatic Series
Start Date: 5/1/17
Wrap Date: 11/16/17
City: Atlanta
City: Senoia

You can view the entire PDF here: http://www.dga.org/~/media/Files/Production List/CPLBAFull pdf