not sure if this works. Give it a try.
But i think it is possible to create multible Wireless Networks with the same SSID.
So in your Case you just copy your existing WLAN (same Settings, same SSID). Only change your schedule. With WLAN-Groups and AP-Group you can get this WLAN only on specific APs.
If you are working with DPSKs and want that your user are able to roam between the Sites, this may not work like expected because DPSK is always bounded to a specific WLAN.
Multible Wireless Networks on a End-User-Device with different PSK is not possible.
With a classic WPA2 PSK Network this should work.
Maybe it helps
Thanks and KR