Need a recurring date field for service businesses to advise on their invoice what the next service date is

Need to tell my customer on the invoice what the date of their next service is, and it needs to automatically show the next date, based on weekly, fortnightly, 3-weekly, 4-wkly etc.  Like a terms field, where you set the terms and it automatically tells you the date due.  This is the same, except it tells the customer when their next visit is.  Based on a selected recurring cycle.  So that we don't have to look up the date and write it in each time.  It just knows what the date will be in two weeks from invoice date.