It+时间+从句”考点透视
请看下面一道题:
The field research will take Joan and Paul about five months; it will be a long time _____ we meet them again.
A. after B. before C. since D. when
这是2007年安徽的一道高考题，其实质上是通过“it + be+从句”这一句型来考查了连词的用法。在该结构中连词的选择是有规可循的，主要是由主句、从句中的谓语动词的时态来确定的。下面通过下表比较（尤其是对主从中时态的比较）就能很容易的掌握。
结构 从句中谓语动词的形式 It is +时间段+since从句 一般过去（到现在为止）做It is three years since the war 时 某事已有多长时间broke out. 了 It was+时间段+since过去完成（到过去某时为从句 时 It was two years since he had 含义 例句 止）做某事已有多left here. 长时间了 It was +时间段+before从句 It was not +时间段+before从句 It will be +时间段+before从句 一般过去过了多长时间时 才…… It was a long time before I got to sleep again. It wasn’t long before he told me about this affair It will be five years before we meet again. It won’t three hours before he arrives at the bus stop. 一般过去没过多长时间时 就…… 一般现在要过了多长时间时 才…… It will be not +时间段一般过去没过多长时间+before从句 时 就…… It is/was +时间点+when引导的定语从句 It is/was+时间状语+that引导的强调句 It’s time that+从句 做某事的时间是什It was eight o’clock in the 么时间 morning when he went shopping. 正是在某个时间，It was at eight o’clock in the 某事发生了 morning that he went shopping. 一般过去是该做某事的时候It is time that I went (should 时（或should+动词原形） 了 go) to pick up his daughter. It is the 现在完成某人第一/二/三次It is my first time (that) I have 做…… visited the Great Wall. first/second/third time 时 +that从句 It/This/That was the 过去完成某人第一/二/三次It was the second time that the first/second/third time 时 +that从句 总结一
在\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.
2. It may be five or six years before the new medicine is tested on human beings. 3. It was two months before he designed the bridge.
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。
做…… film had been shown in this cinema 例如：1. It will be ten days until my birthday comes.
2. It was only five minutes until her husband came back from work.
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. 2. It has been three years since they got married.
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.
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.
2. What time was it when you got to school?
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. 2. It was yesterday afternoon that I met him in the street.
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. 2. It was the third time that he had asked the same question.
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\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. 2. It is time that he left the place. 【链接训练】
例1：It is almost five years_____we saw each other last time.(05北京)
A.before B.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
总结二
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. It is three years since she was in our class.
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.
例2：It will be midday when they get home.
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
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.have arrived D.had arrived 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
(完整版)It+时间+从句的区别完整解释
