Trigger a workflow based on TIME

Hi team,

So I have 2 Entities: Event and Event Schedule

Event has a Start Date and End Date

Event Schedule has Service Start Date/Time and Service End Date/Time.

Event (1) : Event Schedule (N) relationship

I want a workflow to fire off a notification to a user if the Event Schedule Service End TIME is past 8:01 PM. 

How do I get that to work?

Thanks!