Happy to integrate and include it. I've created an issue on GitHub at https://github.com/gerickson/opencflite/issues/45.
I haven't historically leveraged that aspect of functionality in CoreFoundation in my consuming projects, so I can't speak to it. Consequently, I don't have any good examples or functional or unit tests for that aspect of functionality either. The project would welcome a contribution if you're willing and able.
As far as I can see, any time zone functionality that exists in CFNetwork is a direct dependency, in turn, on CoreFoundation. That dependency would either be satisfied by native CoreFoundation functionality on Apple platforms or provided in a package like opencflite. As far as I know, such functionality works in opencflite. However, if not, an issue should be filed against it on GitHub.
OpenCFLite v635.21.1 has been released on GitHub at https://github.com/gerickson/opencflite/releases/tag/opencflite-635.21.1 with the following changes: Applied upstream Apple patches from CF-635.19 to CF-635.21. Applied upstream Apple patches from CF-635.15 to CF-635.19. Addressed a warning/error about the unknown type name of 'CFStreamError' when compiling against the project on Linux. Address a warning/error about the redefinition of 'struct timespec' when compiling against the project on Linux....
Would you be willing to contribute your work to opencfnetwork at https://github.com/gerickson/opencfnetwork?
A new active clone / fork of OpenCFLite is now being hosted on GitHub at https://github.com/gerickson/opencflite/