Chinese-all-day-breakfast/MD/g1-26.md

The use of the time-words 以前 and 以後

When used by itself, 以前 means "previously" or "before" and 以後 means "later", "afterwards" or "in the future":

我以前是學生﹐現在是老師。
    I was a student before; now I am a teacher.
你以前在哪兒工作﹖
    Where did you work before?
以前我不住宿舍﹐現在住宿舍。
    I did not live in a dormitory before, but now I do.

When used together with a time-word or verb phrase, 以前 means "before..." and 以後 means "after...":

十點以前我不回家。
    I won't go home before 10.
回家以前我在閱覽室看書。
    I read books in the reading-room before I go home.
來美國以後他在這兒工作。
    He has been working here after he came to America.
十點半以後你在宿舍作什麼﹖
    What do you do in your dorm after 10:30?

N.B. When 以前 or 以後 is used together with a time-word or verb phrase to mean "before" or "after", the word order is exactly the opposite of the English equivalent:

四點以前
    before 4 o'clock
下課以前
    before the class is over
明天晚上以後
    after tomorrow evening (or night)
回宿舍以後
    after returning to the dormitory