Gives, as free text (the DESCRIPTION itself notes it's a string, not a timestamp type), when the currently loaded filter was installed on the gateway. This is what an admin checks after a policy push to confirm the install actually landed at the expected time, or to spot a gateway that's been silently running a stale policy for weeks. Example: fwFilterDate showing a date three weeks older than the rest of the cluster's gateways reveals that one node missed the last policy install and is still enforcing outdated rules.