Is there anyway I can schedule a Workflow rule/process builer to execute at a specific time of the day everyday, rather than running when something happens to a record(created/updated).

scenario - I want to find out all the cases that are not closed, 7 days after they are created. I would like to then update the field priority to high.

Workflow rules/process builder executes only after a record is either created or updated but what if I want to take action on all records matching a criteria, repeatedly everyday.  

Thanks
Mahesh