If you have a blank display this indicates there is some sort of electrical problem (wiring, fuse, etc.) Check to ensure the outlet the controller is plugged into is operational. Try another electronic device in the outlet or try the controller in another outlet. If the outlet is a GFI plug, check the reset button. Newer controllers have computer components that may need to be rebooted after a power surge. Unplug for 10 minutes to reset. If none of these restore operation, you will need to set up a service appointment. If you have a controller that is more than 10 years old it is likely time for a replacement. 

NOTE:  If your controller display is still functioning (showing appropriate time/date) or counting down the run time but your sprinkler isn't running check this article.