Change QoS Speed Limit / Throttle by time of day

Overnight we would like to increase the bandwidth for some of our devices given there are less other users in the office. If everybody was connected to a GLiNet router we could use QOS to prioritise, but sadly there are plenty of users on the WAN side of the router, hence a speed limit on the router is the easiest solution to maintaining internet access for the whole office.

I can set it in the Clients page of the router admin panel, and have installed luci-app-qos but I cant see anything relating to time of day (including looking here). Could I do it as a scheduled/cron job? I havent been able to find any commands which change QoS speed limits for a certain IP/MAC (which I could run with cron).

Any ideas or help would be very much welcome!