Some of the solar
panel controllers have quite sophisticated controlling options.
For example they can be made to automatically switch a pump on for 3 hours between 10 and 1, but only if its over 10 C and there is diesel
in the tank.
Altering the parameters is not easy because it buried in the menu structure of the controller, but there is enough versatility, and multiple conditions, that you can pick appropriate parameters so the process is automated and does not need to be normally adjusted.
controllers that will do this are not cheap, but if you have solar it may be worth updating to a controller that will do this. The controller could even be installed without any solar panels
, but its expensive just for the timer functions.
Anyway its an option to consider if you want an intelligent timer.