git checkout `git rev-list -1 --before="Sep 19 2019 00:00:00" master`
To apply the command to every subfolders (maxdepth 1)
find . -maxdepth 1 -type d -exec sh -c 'cd "{}" && git checkout `git rev-list -1 --before="Sep 19 2019 00:00:00" master`' \;