public static function propertyIsValid($property_name, &$property_value, &$error)
 {
     if (!parent::propertyIsValid($property_name, $property_value, $error)) {
         return false;
     }
     return true;
 }
 public static function propertyIsValid($property_name, &$property_value, &$error)
 {
     if (!parent::propertyIsValid($property_name, $property_value, $error)) {
         return false;
     }
     if ($property_name === EVENT_TYPE_BIRTHDAY_KEY_DATE_OF_BIRTH) {
         //	Date of birth is a date
         //
         if (UniversallyUniqueObject::propertyIsValid(UNIVERSALLY_UNIQUE_OBJECT_KEY_DATE_CREATED, $property_value, $error) == false) {
             return false;
         }
     }
     return true;
 }
 public static function propertyIsValid($property_name, &$property_value, &$error)
 {
     if (!parent::propertyIsValid($property_name, $property_value, $error)) {
         return false;
     }
     if ($property_name === EVENT_TYPE_ANNIVERSARY_KEY_YEAR) {
         //	Year isn't valid
         //
         if (is_numeric($property_value) && is_int($property_value)) {
             $error = Error::withDomain(VALIDATION_ERROR_DOMAIN, VALIDATION_ERROR_CODE_INVALID_PROPERTY, $property_name . " should be a valid year.");
             return false;
         }
     }
     return true;
 }