有两种用法：一种是接主语+should+动词原形；一种是主语+动词过去式；两种结构可以互换的,是虚拟语气中的知识。还有一种结构就是it is high time+to do sth,不是虚拟语气。
it's high time的用法it's high time和should+动词的连用
It's high time that...是应立即做(某事)的时候了，早就到了做什么的时候了。high time：正是时候,早该。
should表示义务、bai责任、建议或劝告，有“应当、应该”的意思。
It is (high) time that后面的从句，谓语动词要么用过去式或者用should+动词原形，但should不可省略，这是虚拟语气的用法。两者意思一样。意思是：“是某人做什么什么的时候了”
两者的例句如：
1、It is high time that the children went to school.
2、It is high time that the children should go to school.
it's high time例句1、It's high time that you started working.
你早该开始工作了。
2、It's high time to try it.
这是该试一试的时候了。
3、It's high time you left home for work.
你真该离家去上班了。
4、It's high time that we should take action to protect the water resources.
是我们采取措施保护水资源的时候了。
5、I love the old barter system, it's high time to bring it back.
我喜欢旧的易货制度，现在是非常适合的时候把他们带回来。
