searching a solution for time limited guest authorization

I'm searching for a time limited credential-creation for guests. Kind of "valid until 6 PM" one time auth codes. Ideally for a second SSID. We're using Watchguard Access Points managed with a Watchguard Firebox Firewall which already allows detailed tuning of IP ranges and port blocks. The Watchguard would manage the IP subnets for a clean line between guest and standard user. PFsense looks like the Watchguard functions, just on a software basis. So that seems to be a bit "too far in..." Do you have ideas on how to realize that? I'd say we need an internal website where we can click on and then given access data "until 6 PM". Yours, Konstantin