一Itis(hasbeen)+时间段+since+clause(1)在于since前后句子的时态.since前的时态为is或hasbeen，后的时态为一般过去时Eg:Itis(hasbeen)tenyears since I joined the army译为: 我参军已经十年了.(2) since后的动词若为延续性或状态性动词，应译为否定或相反，若为短暂性动词按字面意思翻译.Eg:1It is(has been) ten years since I left the army=It is(has been) ten years since I left the army译为: 我复员十年了.It is ten years since I smoked=It is ten years since I stopped smoking译为: 我戒烟十年了.二It will be(was)+时间段+before+一般现在时态的clause(一般过去时)此句型和句型(一)的共性都加时间段，差异在于前后的时态和翻译Eg:It will be ten years before I return home.译为:要过十年我才能回家.It was ten years before he found his lost boy.译为:过了十年他才练习:找到了他失踪的儿子.三It will be(was) +时间点+when+一般现在时态的clause(一般过去时)和句型(二)比较:前后时态一致，但此句型中为时间点而非时间段Eg:It will be midnight when I return home.译为: 我回到家的时间将是午夜.It was noon when the accident happened译为: 事故发生时已是正午.四It is(was)+时间点+that的强调句型与句型（三）比较时间前通常有介词且去掉it is(was)……that之后句子仍然成立。Eg:①It was in the morning that I was robbed in the street.=It was this morning that I was robbed in the street.②It was at 7:00 that I met Tom this morning.=It was 7:00 when I met Tom this morning.瑞兹学校