Ii\'s time 后面为什么要跟动词过去时

是强调语气的说法，也是英语里一种特殊语法。
例如：It's (very\high) time took the responsibility. 是成都责任是时候了。

谁说的？
通常是

It's time to do something.

表：现在应该去做某事

是虚拟语气
IT'S TIME WE WENT THERE.(我们早就该走了)
表示早就应该做某事,现在终于要做了.
IT'S TIME (THAT) WE DID=IT'S HIGH TIME (THAT) WE DID=IT'S ABOUT TIME (THAT) WE DID