How you set your watch depends not only on the neighborhood, but on your profession and ethnicity, religion and loyalty.
People living on both sides of the time divide say there is little confusion because they have as little to do with each other as possible.
When communist China was formed in 1949, Mao Tse-tung decreed that everybody should follow a single time zone, no matter that the country is as wide as the continental United States.
But Uighurs, the dominant minority in China's northwestern Xinjiang province, balked at running their lives on Beijing time, which would have them getting up in the pitch dark and going to sleep at sunset.
"It is as ridiculous as having Los Angeles following New York time," said Alim Seytoff, who left Xinjiang in 1996 and is now secretary-general of the Uyghur American Assn. in Washington.
"That is the totalitarian nature of the Chinese government that they try to impose one time zone."