时间状语从句是一种使用频率极高的状语从句，也往往是学习状语从句的第一步。很多人看到各种变化的时态和丰富的连词就开始觉得晕头转向了，但实际上时间状语从句并不难学，它的各个连词都是生活中常见的英语单词，只要记住它们遵循的时态原则，就能慢慢掌握了。所以这次沪江小编就为大家整理了一些连词的用法，希望能给大家带来帮助。

用表示时间的连词连接一个句子作状语，这样的主从复合句就是时间状语从句。

常用的连接词有：when, while, as;before, after;as soon as, hardly...when..., no sooner...than...;till, until;since;by, by the time, by the end of。

一. when、while和as: “当...时候”

when引导的从句的谓语动词可以是延续性的动词，也可以是瞬时动词，并且遵循主将从现原则：

eg. When she comes, I will tell her the bad news.

While引导的从句的谓语动作必须是延续性的，并强调主句和从句的动作同时发生（或者相对应），也可以表达对比的意思。

eg. While my wife was reading the newspaper, I was watching TV. (同时发生)

     I choose this one while you choose that one.（对比）

As表示“一边……一边”，as引导的动作是延续性的动作，一般用于主句和从句动作同时发生，as也可以强调“一先一后。

eg. We always watch TV as we have dinner.（as表示“一边……一边”）

     As we were going out, it began to snow.(我们下出门，再下的雪）

二. before,after: 表示时间先后，遵循主将从现原则, 在表达过去时，before所在的从句谓语动词要使用一般过去时，其主句谓语动词要采用过去完成时，而after所在的从句谓语动词要采用过去完成时，其主句谓语动词要采用一般过去时。

eg. It will be four days before they come back.

     After she had arrived home, it began to rain.

     Before it began to rain, she had already arrived school.

     After she had arrived school, it began to rain.

三. till和until：“直到....”, 一般情况下两者可以互换，till多用于肯定句，untill多用于否定，untill还可用于强调句。

eg. I didn't go to school until（till） my teacher called my parents.

     It was not until he came to my home that I started go out my room.

四. since: "自从"，一般情况下，从句谓语动词用一般过去时，而主句的谓语动词用现在完成时。

eg. I have been in Beijing since 2012.

     It is four years since I lived in Beijing.

好了，以上就是这次沪江小编为大家带来的内容，大家都看明白了吗？ 综上所述我们可以看出，时间状语从句里最重要的就是时态的使用，即使是意思相同的连词，甚至是同一个连词，因为时态的不同也会导致意思的不同，学习者们需要格外注意。