Workflow Rule and Alert for expiring contract

Workflow Rule and Alert for expiring contract

I need to define a rule that allows me to set an alert notifying concerned parties within our company that a contract expiration is approaching in 90 days and they need to renew the service agreement.  Currently, I don't see a way to do this.  I have created a Contract End Date field within each account.  So, the rule needs to be something like Contract End Date = Today+90days.  Alert is: IF (Contract End Date = Today+90days), SEND ALERT NOTIFICATION EMAIL.

Please advise.  Thanks.