2.3.4. How often should a client update its time zone definition
2.3.4.1.
Clients can compare a checksum of its time zone list against the server’s checksum, if it’s different; the client refreshes its time zone list with the server’s time zone list.
2.3.4.2.
By doing periodic checks on the server.
2.3.4.3.
Using a push mechanism notifying the client that a time zone has been updated. Possibly by adding a new iTIP method.