American time, Gregorian calendar, 1972.7. 10.5:00 to 6:00 pm. When did conversion of time become China?

The United States has four time zones, unlike China, which only has Beijing time. July 10 is American daylight saving time. There are at least four answers to this question (excluding Alaska and Hawaii).

So 1972 July 10, 5 pm -6 pm:

① If it is the Pacific time zone (representing Los Angeles), Beijing time is 8: 00-9: 00 a.m. on July 6th11;

② If it is a mountainous time zone (representing the city where Salt Lake City is located), Beijing time is 7: 00-8: 00 a.m. on July 1 1;

③ Central time zone (representing Chicago), 6: 00-7: 00 am Beijing time on July 1 1;

④ Eastern time zone (representing the cities of new york and Washington), 5: 00-6: 00 a.m. on July 6th, Beijing time1/.