一般过去时的时间状语：yesterday, last week，…ago, in1980, in October,just now等，皆为具体的时间状语。
现在完成时的时间状语：for, since, so far, ever, never, just, yet, till/until, up to now, in past years, always等，皆不确定的时间状语。
共同的时间状语：this morning, tonight, this April, now, already, recently, lately 等。
3) 现在完成时可表示持续到现在的动作或状态，动词一般是延续性的，如live,teach, learn, work, study, know.。
一般过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。例如：
I saw this film yesterday. （强调看的动作发生过了）
I have seen this film. （强调对现在的影响，电影的内容已经知道了）
Why did you get up so early? （强调起床的动作已发生过了）
Who hasn't handed in his paper? （强调有卷子未交，疑为不公平竞争）
He has been in the League for three years. （在团内的状态可延续）
He has been a League member for three years. （是团员的状态可持续）
注意:句子中如有过去时的时间副词（如yesterday, last, week, in 1960）
（错）Tom has written a letter to his parents last night.
（对）Tom wrote a letter to his parents last night.
1）It is the first / second time … that… 结构中的从句部分，用现在完成时。
例如： It is the first time that I have visited the city.
This is the first time （that） I've heard him sing.
注意：It was the third time that the boy had been late.
2） This is +形容词最高级+that…结构，that 从句要用现在完成时。
例如： This is the best film that I've （ever） seen.
（1） ---Do you know our town at all?
---No, this is the first time I ___ here.
A. was B. have been C. came D. am coming
答案B. This is the first time 后面所加从句应为现在完成时，故选B。
（2） ---Have you ____ been to our town before?
---No, it's the first time I ___ here.
A. even, come B. even, have come C. ever, come D. ever, have come
（错）I have received his letter for a month.
（对）I haven't received his letter for almost a month.
例如： I have lived here for more than twenty years. 我住在这儿二十多年了。 (延续)
I have lived here since I was born. 我从出生起就住在这儿了。(开始时间)
I worked here for more than twenty years. （我现在已不在这里工作。）
I have worked here for many years.（现在我仍在这里工作。）
1）（对） Tom has studied Russian for three years. = Tom began to study Russian three years ago, and is still studying it now.
2）（错） Harry has got married for six years. = Harry began to get married six years ago, and is still getting married now.
显然，第二句不对，它应改为 Harry got married six years ago. 或 Harry has been married for six years.
1） since +过去一个时间点（如具体的年、月、日期、钟点、1980, last month,
half past six）。
例如： I have been here since 1989. 1989起，我一直在这儿。
2） since +一段时间+ ago。
例如： I have been here since five months ago.
3） since +从句。例如：
Great changes have taken place since you left. 你走后，变化可大了。
Great changes have taken place since we were here.
4） It is +一段时间+ since从句。例如：
It is two years since I became a postgraduate student.
He has completed the work. 他已完成了那项工作。 （表结果）
I've known him since then. 我从那时起就认识他了。（表经历）
2） 用于till / until从句的差异
延续动词用于肯定句，表示"做……直到……" 瞬间动词用于否定句， 表示
He didn't come back until ten o'clock. 他到10 点才回来。
He slept until ten o'clock. 他一直睡到10点。
1. You don't need to describe her. I ___ her several times.
A. had met B. have met C. met D. meet
2. ---I'm sorry to keep you waiting.
---Oh, not at all. I ___here only a few minutes.
A. have been B. had been C. was D. will be