当英语中的时间状语位于句首时，通常需要进行倒装，以强调时间或情境。基本规则是将助动词或情态动词放在主语之前。如果句子中没有助动词或情态动词，需要添加do/does/did等助动词。特殊的时间状语，如"only", "never", "not until"等，需要特殊处理。
什么是时间状语？
时间状语是指描述时间的单词或短语，包括日期、星期、季节、年份、时间段等等。例如：yesterday, last week, in the summer, on Monday, at noon等等。
倒装的基本规则
在英语中，当句子以时间状语开头，动词需要与主语进行倒装，即将助动词或情态动词放在主语之前。
例如：
- Yesterday, I went to the cinema. → Yesterday, went I to the cinema.
- In the summer, they often go to the beach. → In the summer, do they often go to the beach.
- At noon, we will have lunch. → At noon, will we have lunch.
需要注意的是，当句子中没有助动词或情态动词时，需要在句子中添加do/does/did等助动词。
例如：
- In the winter, it snows a lot. → In the winter, does it snow a lot.
- Last week, she bought a new car. → Last week, did she buy a new car.
特殊情况
有些时间状语需要特殊处理，比如：
- Only后置：Only when he arrived did I realize my mistake.
- Never后置：Never have I seen such a beautiful sunset.
- Not until后置：Not until I finished my work did I go to bed.
在这些情况下，倒装的助动词或情态动词需要放在时间状语之前，并且主语仍然位于动词之后。
