My goal is to have a field in a contacts that will when triggered will automatically send a reminder to our customers to think about buying a certain item.  This reminder e-mail is to be triggered every September.  I want this to automatically do this every year moving forward.

The problem is that I tried using a check box but, there is not way that I see, to set it to send only once every September.

Suggestions on 
1) What field to add

2) How to create that automation 

Is this possible?

Thanx,
PK