I appeal to those readers of the mailing list capable of reading Chinese / mandarin to look for sources which could
- document that multiple timezones where indeed maintained before May 1980 (e.g. railway or airline time tables of that period),
- document the transition to a unified zone in May 1980 (legal text, newspaper articles mentioning the time change)
- document the government decision for a unified timezone in 1949

My gut feeling is that the unified timezone was introduced in 1949, and that Shanks got it wrong. We need documents to establish that.