This looks like either a local issue (did you validate your clock?) or perhaps some local cache that causes issues?
The certificates that were deployed on July 19th (when you sent this report -- sorry for the late responses) all had expiry times on Sep 22 or Sep 23, and are the same ones that are deployed now.
If you can still reproduce this issue on your site, please include the full details of the certificate that has expired, and we can do some further investiation.