This understandably causes problems in the far western provinces such as Xinjiang, so everyone just observes an unofficial GMT+6 time instead. This wreaks utter havoc on conversationd about time: bus schedules, shop opening hours, etc. Aside from the ambiguity, since it's not an official time zone, people overseas just assume they can call you to discuss business at 9am, even though you've barely woken up.
Time zones are complex because, well, the world is a big and complicated place. But theanswer is certainky not to just get rid of them!
Add metadata to all phone records that makes it easy to specify and query the hours in which one would like to be called.