Can a formula be written to have a date automatically update dependent on information in two other fields?

I am good with not having a history of prior expiration.  A lot renew on a monthly basis automatically, however some renew automatically yearly or every 5 years.  I would like the expiration date to automatically update based on if the contract auto-renews (current field, could change to a check box if that would make the formula easier) and the number of days indicated in the renewal days (current field).