If you have an error message that reads something like this: "Error reported from RE on saving the record from the area map "Constituent". The reported error was: Date to cannot be before Date from.", you will need to open the mappings for that area (in this example it would be mappings connected to "Constituent" and look to resolve why a Date To is before a Date From.
Most of the time, when this occurs, it is because there is an Address or a Constituent Code mapping that has the Date To field filled in rather than the Date From field.
This may also happen if Importacular is updating a historical address (check your address match settings if you believe that to be the case and adjust them accordingly). If you are updating addresses that already exist in the Raiser's Edge and that have a "Date To" populated in the Raiser's Edge, you may find the Address Area Setting option to remove the "Date to" on existing addresses (shown unchecked below - to use you will need to check the box instead) helpful.