Together, a very literal and logical combination emerges: 那 (that) + 时候 (time/moment) = 那时候 (that time / that moment).
While “at that time” is a simple concept, `那时候` is a powerful key that unlocks a very common cultural practice in China: reminiscing about the past to comment on the present. Older generations frequently use `那时候` to introduce stories comparing the hardship of the past with the prosperity of today. A common topic is life before the “Reform and Opening-Up” policy (`改革开放 gǎigé kāifàng`) that began in the late 1970s. You'll often hear sentences starting with, “那时候我们很穷,但是很快乐” (“Back then we were poor, but we were very happy”). This isn't just idle nostalgia. It's a way of expressing core cultural values: appreciating progress, valuing resilience, and teaching the younger generation not to take modern conveniences for granted. While Americans might say “back in my day” to talk about walking to school uphill both ways, the Chinese use of `那时候` is often tied to a specific, dramatic, and collective national transformation that is still within living memory. It connects personal stories to a much larger national narrative.
`那时候` is an incredibly common and versatile phrase used in almost any context, from casual chats to more formal speeches.