在表示时间的单词前有:every, last, next 等单词时.例如:
1. I get up early every morning.= I get up early in the morning every day.
2. I was late for classes last week.
3. He will help me next Monday.
在上述例句中的时间短语前都不能再用其它介词
我再补充一种情况,就是ago
例如, I went to beijing two weeks ago.