Calls the get_timezone_sync method on the given backend.
This method is not mandatory on the backend, because here is used internal_get_timezone call to fetch timezone from it and that is transformed to a string. In other words, any object deriving from ECalBackendSync can implement only internal_get_timezone and can skip implementation of get_timezone_sync completely.
| this |
An ECalBackendSync object. |
| cal |
An EDataCal object. |
| cancellable |
a Cancellable for the operation |
| tzid |
ID of the timezone to retrieve. |
| tzobject |
Placeholder for the returned timezone. |