高考It +be+ 时间 + 从句”结构
总结一
在“ It +be+ 时间 + 从句”结构中，引导从句的从属连词有 before, that, since, until （ till ） , when 等。这一结构是近几年高考常考的知识点，现将它们的用法小结如下：
一、 It +be （ not ） + 时间段 +before 从句。
其中的主句是肯定式时，意为“过多长时间才……”；主句是否定式时，意为“没过多久就……”。例如：
1. It was not long before the whole country rose and drove the Austrian soldiers from their homeland. 不久，全国人民便奋起反抗，把奥地利军队从他们的国土上赶了出去。
2. It may be five or six years before the new medicine is tested on human beings.
要过五六年时间这种新药才能在人身上做试验。
3. It was two months before he designed the bridge. 过了两个月，他设计出了这座桥梁。
二、 It +will be （ was ） + 时间段 +until 从句
若主句中用一般将来时，则从句中用一般现在时，意思是从现在起到从句中谓语动词表示的动作发生时还有多长时间；若主句中用一般过去时，则从句中也用一般过去时，意思是从过去某一时间起到从句中谓语动词表示的动作发生还有多长时间。例如：
1. It will be ten days until my birthday comes. 到我生日还有十天。
2. It was only five minutes until her husband came back from work.
当时离她丈夫下班只有五分钟了。
注意：结构“一”与结构“二”在肯定句中几乎可以通用。但是，若从句中谓语动词表示的将来动作一定或预期肯定会发生，则多用 until 引导从句；若从句中谓语动词表示的将来动作在客观上并非一定要发生时，则多用 before 引导从句。
三、 It +is / has been （ was ） + 时间段 +since 从句
在这一结构中，主句常用一般现在时、现在完成时或一般过去时。如果 since 引导的状语从句中的谓语动词为非延续性动词，则表示“自从状语从句中的动作发生以后，时间过不了多久”。例如：
1. It is two years since Jim came to China.
吉姆来中国两年了。
2. It has been three years since they got married.
他们结婚已经三年了。
如果 since 从句中的谓语动词为延续性动词，则表示“自从从句谓语动词表示的动作结束以来，时间已过了多久”。例如：
3. It is / has been a year since he smoked.
他戒烟已经一年了。
四、 It +is / was + 时间点 +when 从句
在这一结构中，时间之前没有介词，从句为 when 引导的时间状语从句。从句常用一般过去时，意为“当某事发生时，时间是……”。例如：
1. It was October 1st, 1949 when the People's Republic of China was founded.
中华人民共和国成立于 1949 年 10 月 1 日。
2. What time was it when you got to school?
你几点到的学校。
五 . It is /was + 时间状语 +that 从句
这是一个强调句型，被强调的部分是时间状语。表示“正是在某个时间，某事发生了”。例如
1. It was ten years ago that he joined the army. 他正是在十年前参的军。
2. It was yesterday afternoon that I met him in the street.
就是在昨天下午我在街上遇见了他。
六、 It is / was +first time / second time + （ that ）从句
在这一结构中， time 前面常用序数词来修饰， that 引导的是定语从句，从句中常用现在完成时态或过去完成时态，表示“这是第……次做某事”。例如：
1. This is the first time in my life that I have come to Beijing.
这是我一生中第一次来北京。
2. It was the third time that he had asked the same question. 这是他第三次问同一个问题。
七、 It is （ high ） time +that 从句
在这一结构中， that 从句中的谓语动词常用虚拟语气，即“ should + 动词原形”或用动词的过去式，表示“该做某事了”。例如：
1. It is high time that we began our work. 我们该开始我们的工作了。
2. It is time that he left the place. 他该离开那个地方了。
“It +be+ 时间 + 从句”结构
总结二
例1：It is almost five years_____we saw each other last time.(05北京) A.beforeB.since C.after D.when
例2：-Did Jack come back early last night？ -Yes.It was not yet eight o‘clock________he arrived home. A.before B.when C.that D.until
例1.正确答案：B 我们已经有5年没见面了。
例2.正确答案：B 他回家时还不到8点
这类考题出现频率较高，考生又极易混淆，在复习中做出归类非常必要：
1.It is/has been + 时间段 + since + 一般过去时
例1：It is/has been 10 years since he came here.这类句型可转化为： =Ten years has passed since he came here. 这一句型可扩展为：It was+时间段+since(从句用过去完成时)
例2：It was years since he had arrived in China.(过去是+since+过去完成时) 需要注意的是since从句的谓语动词一般是非延续性动词，但有时也可用延续性动词或表示状态的词，此时需要注意句子的翻译：
例3：It is three years since she came to our class.她来我们班已经有三年了。 It is three years since she was in our class.她离开我们班已经有三年了。
2.It + was + 时间点 + when clause(从句谓语用一般过去时) will be+时间点+when clause(从句谓语用一般现在时表将来)
例1：It was already evening when he came back.当他回家时已经8点了。
例2：It will be midday when they get home.当他们到家时将是中午。
3.It + will(not) be + 时间段 + before + 现在时 was(not)+时间段+before+过去时
例1：It will be another year before he comes here.
例2：It was some time______we realized the truth.(2005山东24) A.when B.until C.since D.before
例2：正确答案：D。过了一段时间后我们才了解了真相。 该句型中before前常用时间段，表示“…之后才…”“在…之前就…”;有时before前也可以用时间点，此时突出表示动作的变化。试比较：
例3：It was evening before we reached the little town of Tailstocks. 当我们到达Tailstocks时已经黑了。(到达前天还没有黑)
4.It/This is + the + 序数词 + 时间 + 定语从句(从句用完成时)
例1：It is the first time (that) I have been here.(定语从句) 该句型可扩展为：It was+序数词+时间+定语从句(从句用过去完成时)
例2：It was the second time he had been out with her alone.
例3：It’s the second time you________late this week. A.arrive B.arrived C.havearrived D.hadarrived 正确答案：C。这是这个星期你第二次迟到了。
5.It is + (high)time + that + did(虚拟语气)
例1：It is (high) time (that) we stopped pollution. 其中that引导得从句中也可用should+V(原型)
例2：It is (high) time (that) you came/should come here. 写作中表示建议时也常可用这类句型。
例3：It‘s high time we took measures to solve this problem.
注意应将以上5种句型与强调时间的强调句型的区别。
6.It be + 时间(被强调部分) + that
例1：It was at 6 o’clock that we heard the noise.
例2：It was 3 years ago that he joined the army. 最简单的判断方法是：当表示时间的词前有介词或者后有副词时，一定是强调结构，必用that。 试比较下面句式与强调句的不同之处： It was already ten o‘clock when he arrived. It is ten years since I met you last. It was quite some time before he found the elephant at all. 以上几句中时间前无介词后没副词故不是强调句型。
《动手练一练》： 1.It was not until 1936________basketball became a regular part of the Olympic Games. A.that B.when C.which D.then
2.It will not be________we meet again. A.long before B.before long C.soon after D.shortly after
3.──He was nearly drowned once. ──When was________？ ──________was in 1998 when he was in middle school. A.that;It B.this;This C.this;It D.that;This
4.It was evening________we reached the little town of Winchester.(04天津) A.that B.until C.since D.before
5Scientists say it may be five or six years_it is possible to test this medicine on human patients. A.since B.after C.before D.when
6.It was______I met Mr.Smith in London.
A.many years that B.for many years since C.since many years ago when D.many years ago that
7.-What was the party like？ -Wonderful.It‘s years_____I enjoyed myself so much.
A.after B.before C.when D.since