高中英语常见的一种句型，请帮我分析下。纠结好久了！

Question

It is at time that sb did sth.
It is time when sb did sth
It is time that sb did sth
It time for sb to do/

Answer 1

It's time + that clause 时，that可省略，time可由high,about修饰，从句中的谓语动词有两种形式，或者用动词的过去式(be用were); 或者用shoud + 动词原形（should不能省略)。此句型为虚拟语气句型，表示“现在某人该做某事了”。
含有该事早该去做而未做，现在去做似乎都为时已晚的意思。例：

1.It's time （that）we went to bed. 我们该去睡觉了。

2.It's high time that the article were published.发表这篇文章是适时的。

3.It's time you should do cleaning. 你该去打扫卫生了。

It is time that sb did sth. 这本身就是【定语从句】。这个句式也不适合改为强调句。
time的常用句型有：
It is time to do sth
It is time for sb to do sth
It is time for sth
It is time( that) sb did sth
should do sth 最后这两种形式，都是表示【虚拟语气】的句式。
例如：
It is time that I worked harder for my dream.
=It is time that I should work harder for my dream.
该是我为我的梦想而努力的时间了。（表示“幡然悔悟，早该努力”）。
对比【强调结构】：
It was【 at six o'clock yesterday时间状语，被强调部分】 that I met him at the school gate.
It is 【him】 that /whom I met at six o'clock yesterday at the school gate.
强调句型判断：去掉It is ...... that 后，句子是完整的 才是强调句

Answer 2

都是到时去做某事的意思，结构不同

Answer 3

最后一个是单句 倒数第二个是从句，用虚拟语气 倒数一二意思一样，到某人做某事时间了。正数第二 当某人做事时间是……时间状语从句