Assistance: Need to Send a Group of Users a Certain E-Mail on the 27th of Each Month

Assistance: Need to Send a Group of Users a Certain E-Mail on the 27th of Each Month

I am sure the solution is simple, but I cant seem to find my brain at the moment.  Here is the scenario.  We want to send our paying customers an automated e-mail on the 27th of each month letting them know their credit card on file will be charged on the 1st of the month for their subscription.  I have the e-mail ready, but cannot figure out what criteria, or exactly which zoho process I need to setup, or what to base it off of, to make this occur.  Any help or ideas would be greatly appreciated.

We currently utilize the Enterprise Edition.  
Brad