1. According to This news report: http://news.sina.com.cn/c/2004-09-01/19524201403.shtml , on April 11, 1919, newspaper in Shanghai said clocks in Shanghai will spring forward for an hour starting from midnight of that Saturday. The report did not mention what happened in Shanghai thereafter, but it mentioned that a similar trial in Tianjin which ended at October 1st as citizens are told to recede the clock on September 30 from 12:00pm to 11:00pm. The trial at Tianjin got terminated in 1920. 2. For the history of time in Shanghai between 1940-1942, the situation is actually slightly more complex than the table included in the tz database now. At the time, there were three different authorities in Shanghai, including Shanghai International Settlement, a settlement established by western countries with its own westernized form of government, Shanghai French Concession, similar to the international settlement but is controlled by French, and then the rest of the city of Shanghai, which have already been controlled by Japanese force through a puppet local government (Wang Jingwei regime) It was additionally complicated by the circumstances that, according to the 1940s Shanghai summer time essay cited in the database, some departments/businesses/people in the Shanghai city itself during that time period, refused to change their clock and instead only changed their opening hours. For example, as quoted in the article, in 1940, other than the authority itself, power, tram, bus companies, cinema, department stores, and other public service organizations have all decided to follow the summer time and spring forward the clock. On the other hand, the custom office refused to spring forward the clock because of worry on mechanical wear to the physical clock, postal office refused to spring forward because of disruption to business and log-keeping, although they did changed their office hour to match rest of the city. So is travel agents, and also weather observatory. It is said both time standards had their own supporters in the city at the time, those who prefer new time standard would have moved their clock while those who prefer the old time standard would keep their clock unchange, and there were different clocks that use different time standard in the city at the time for people who use different time standard to adjust their clock to their preferred time. 2.a. For the 1940 May 31 spring forward, the essay claim that it was coordinared between the international settlement authority and the French concession authority and have gathered support from Hong Kong and Xiamen, that it would spring forward an hour from May 31 "midnight", and the essay claim "Hong Kong government implemented the spring forward in the same time on the same date as Shanghai". 2.b. For the 1940 fall back, it was said that they initially intended to do so on September 30 00:59 at night, however they postponed it to October 12 after discussion with relevant parties. However schools restored to the original schedule ten days earlier. 2.c. For the 1941 spring forward, it is said to start from March 15 "following the previous year's method", and in addition to that the essay cited an announcement in 1941 from the Wang regime which said the Special City of Shanghai under Wang regime control will follow the DST rule set by the Settlements, irrespective of the original DST plan announced by the Wang regime for other area under its control(April 1 to September 30). (no idea to situation before that announcement) 2.d. For the 1941 fall back, it was said that the fall back would occurs at the end of September (A newspaper headline cited by the essay, published on October 1, 1941, have the headlines which said "French Concession would rewind to the old clock this morning), but it ultimately didn't happen due to disagreement between the international settlement authority and the French concession authority, and the fall back ultimately occurred on November 1. 2.e. In 1941 December, Japan have officially started war with the United States and the United Kingdom, and in Shanghai they have marched into the international settlement, taken over its control 2.f. For the 1942 spring forward, the essay said that the spring forward started on January 31. It said this time the custom office and postal department will also change their clocks, unlike before. 2.g. The essay itself didn't cover any specific changes thereafter until the end of the war, it quoted a November 1942 command from the government of the Wang regime, which claim the daylight saving time applies year round during the war. However, the essay ambiguously said the period is "February 1 to September 30", which I don't really understand what is the meaning of such period in the context of year round implementation here.. More researches might be needed to show exactly what happened during that period of time. 3. According to a Japanese tour bus pamphlet in Nanjing area believed to be from around year 1941: http://www.tt-museum.jp/tairiku_0280_nan1941.html , the schedule listed was in the format of Japanese time. Which indicate some use of the Japanese time (instead of syncing by DST) might have occurred in the Yangtze river delta area during that period of time although the scope of such use will need to be investigated to determine. ---- Other information: i. The HKO link reference link in Asia/HongKong have already become inaccessible probably due to site update. The link can now be accessed from https://www.hko.gov.hk/en/gts/time/Summertime.htm