I cannot reproduce this Phillip, so I am going to need a test case that reproduces this. My attempt has exactly what you say you have:

public static class LongToDateConverter implements AttributeConverter<Date,Long> {
    ...
}

@Entity
class AnEntity {
    ...
    @Convert( converter = LongToDateConverter.class )
    private Date theDate;
}

Which reads the database value as a Long, passes it to the converter for conversion just like i asked. Same the other way.