The present day of the book takes place in the 1980's-era San Francisco Bay Area, with a trip at the end to Guangzhou and Shanghai, China. The daughters’ youth therefore takes place somewhere in the 1950’s in San Francisco.
The mothers, however, engage in a series of flashbacks that take place all over China: Wushi, Kweilin, Tai Lake, etc. Their flashbacks also take place across a number of years, ranging from 1920 to around 1940.
The different settings (China vs. America/ first half of the 20th Century vs. the second half) in which the mothers and daughters grew up and spent their youth determines their values and how they relate to world. And these different settings leads to the majority of the confusion and tension between the two generations.
It's also important that the daughters grew up in the U.S. surrounded for the most part by American culture. The American culture and language are unfamiliar to the mothers, making them seem foreign and awkward to the daughters. For the daughters, their only connection to China is their parents.