The Key parameter of the Add method initializes the Key property of the newly created time-zone. The MarkZones collection can not contain two separate MarkZone objects with the same key, so the key should be unique. If you need to change the time-zone's key you can remove and add a new time-zone with a different key. The Remove method removes the specified time-zone. The Item property may be used to access the time-zone object based on its key. The MarkZoneFromPoint property indicates the time-zone from the cursor.