The 'auto' is used to trigger a date on another date field... not for the initial date. So, for example, if you said you wanted the service start date to be 10 days after the date of acceptance, in the acceptance field, you would set up an increment of 10 days and make sure target would be the ID of the service start date... and then set it to auto. That way, when you set the acceptance date, the service start date would automatically default to 10 days later.
To setup, go into Program Configuration...
Click on Edit Dates for the Key Dates...
Setup your date rules...