I'm trying to set-up a workflow to simply send a birthday greeting to contacts on the day of their birthday.
 
Initially I created a custom "Next Birthday" contact field -- Calculates the date of the contact's next birthday (based on Birthdate field).
 
Then, I set up a workflow to trigger when TODAY()=Next_Birthday__c...along with workflow actions to send an email and a task to record the activity.

However, SFDC support explains that only actions (adding or updating records) can trigger a workflow. 

How can I use changes in the current date as a trigger for workflows? Open to any work-arounds.