...
In the filter settings below, the resulting view two advanced filters are used: Last Activity > Greater or equal > 9-1-2020 and Last Activity > Less or equal > 10-31-2020.
Using Greater or equal in the first advanced filter will include all records who's last activity was reported on / after 9-1-2020. Using Less or equal in the second advanced filter will include all records who's last activity was reported before/on 10-31-2020.
The combination of both of these advanced filters will give the user a list of contacts that he has not contacted in the dates between 09-21-2020 and view of leads who's last activity was reported on/after 9-1-2020 and before/on 10-31-2020.
*The dates must be entered as MM-DD-YYYY and not MM/DD/YYYY.
...