QTimeZone' is an incomplete type

The error message "QTimeZone' is an incomplete type" usually occurs when the compiler is not able to find the full definition of the QTimeZone class. This can happen if the required header file is not included, or if there is a circular dependency between header files.

To resolve this error, you can try the following steps:

1. Make sure that the required header file is included in your code. In this case, you should include the "QTimeZone" header file.

2. Check if there are any circular dependencies between header files. If there are, try to resolve them by forward declaring the classes that are causing the circular dependency.

3. If the above steps do not work, try cleaning and rebuilding the project.

If none of these steps work, you may need to provide more information about your code and the context in which the error is occurring.