Wei Yunsi is the keeper of Customs clock on the Customs House, which is one of the most magnificent historic buildings was once called "the symbol of Shanghai" in Shanghai's Bund. / VCG Photo

For 28 years, Wei has to lubricate all the clock gears, wind them up, check the running of the big clock, and proofread the hour at least three times a week. "I can't live without the clock, and the clock can't live without me," Wei used to say. / VCG Photo

To ensure the normal operation of the customs clock, Wei has never left Shanghai for more than twenty years. The error of the customs clock is no more than two seconds in Wei’s career. And now, he is about to retire. / VCG Photo

The Customs Clock, designed and manufactured by a British company, was shipped here from London in 1927, making it the largest clock in Asia and the third largest in the world. / VCG Photo