DDD (Domain Driven Design), how to handle entity state changes, and encapsulate business rules that requires large amount of data to be processed

public class Person
{
    public IList<String> SpecialBirthPlaces;
    public static readonly DateTime ImportantDate;
    public String BirthPlace {get;set;}

    public DateTime BirthDate
    {
        set
        {
            if (BirthPlace!=null && 
                value < ImportantDate && 
                SpecialBirthPlaces.Contains(BirthPlace))
            {
                BirthPlace = DataBase.GetBirthPlaceFor(BirthPlace, value);
            }
        }
    }
}

This is an attempt to encapsulate a simple rule in my domain model. The rule I'm trying to capture is: when, for some reason, we update a person's birth date (e.g. there was a mistake in the original user input) we need to check the person's birthplace and replace it with some other value from a database, if it is listed in our database as a special birthplace.

However, I have 2 problems implementing it:

1. This rule modifies domain entity state (property) and I need to reflect this change in the user interface. My domain model is POCO. I could put this logic in the ViewModel, but this is wrong because it's not UI logic. It's an important domain rule which I need to capture.

2. My list of SpecialBirthPlaces is pretty big and I don't want to populate it every time I get a customer from database. Also, I need to get a replacement for Birthplace when the rule is satisfied. As I said the list of special birthplaces and replacements for this is very big and is stored in the DB.

How to implement the logic I need in DDD style?