since后面的时态有什么规定

当since表示“自从”时，不管它是用作介词、连词还是副词，它通常都要与现在完成时（since前）连用。

当主句表示“多长时间”时，动词可用一般现在时（当然也可用现在完成时）。

相关介绍

Since he changed jobs he's looked like a new man.

他跳槽之后像换了一个人似的。

I haven't seen him since the summer before last.

我已有两个夏天没见过他了。

They've been best friends since they were children.

他们从孩提时起就是最要好的朋友。

He's been working in a bank since leaving school.

他中学毕业以后一直在一家银行工作。

The hotel has polished up its act since last year.

这家酒店自去年以来已经改善了服务水平。