我们很多学生都熟悉It is (high) time that ...这个句型，很多语法书都有介绍。你问题中的句型 It is past time that ... 实际上是从It is high time that这个句型演变来的，它们的用法基本相同，即that后面的从句谓语动词要用过去式或用should加动词原形，但should不可省略。 It is past time that 的意思是“早该...”。 也可以写成 It is long past time that...,it is well past time that...

例句：1. It is long past time that you should visit our English Q & A website.

2.it is past time that the administration established a policy on determining the fates of the detainees at U.S. Naval Base.

2. It is long past time that we should start having opinions of our own.

    在非正式文体中，也有should省略的现象。