These characters combine logically. `后天 (hòutiān)` literally means “after-day,” which is “the day after tomorrow.” By adding `大 (dà)`, or “big,” you get `大后天 (dàhòutiān)`, which can be thought of as “the big after-day”—the one that comes even after `后天`. It extends the sequence in a very intuitive way.
The existence of 大后天 (dàhòutiān) highlights a linguistic difference in how Chinese and English conceptualize the near future. English has specific words for today (“today”) and the next day (“tomorrow”). For two days out, it often uses a descriptive phrase (“the day after tomorrow”), and for three days out, it defaults to a numerical phrase (“in three days,” “three days from now”). Chinese, in contrast, uses a set of discrete, concrete nouns for a longer sequence:
This reflects a preference for specific, established terms for the immediate, plannable future. It's less about a deep philosophical value and more about a linguistic pattern that provides clarity and efficiency when discussing schedules. The symmetrical nature of this system is also seen when talking about the past, with `前天 (qiántiān)` (the day before yesterday) and `大前天 (dàqiántiān)` (three days ago).
大后天 (dàhòutiān) is an extremely common, everyday word used in both spoken and written Chinese.
If today is a Monday, 大后天 is always Thursday. It is a fixed point in time relative to the present day.