Present+Perfect+Tense

=Present Perfect= 

FORM
[S+has/have + past participle] Examples:
 * You **have seen** that movie many times.
 * **Have** you **seen** that movie many times?
 * You **have not seen** that movie many times.

USE 1 Unspecified Time Before Now
e use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important. You CANNOT use the Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We CAN use the Present Perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc. Examples: > B: Yes, there **has been** a war in the United States.
 * I **have seen** that movie twenty times.
 * I think I **have met** him once before.
 * There **have been** many earthquakes in California.
 * People **have traveled** to the Moon.
 * People **have not traveled** to Mars.
 * **Have** you **read** the book yet?
 * Nobody **has** ever **climbed** that mountain.
 * A: **Has** there ever **been** a war in the United States?

How Do You Actually Use the Present Perfect?
The concept of "unspecified time" can be very confusing to English learners. It is best to associate Present Perfect with the following topics:

TOPIC 1 Experience
You can use the Present Perfect to describe your experience. It is like saying, "I have the experience of..." You can also use this tense to say that you have never had a certain experience. The Present Perfect is NOT used to describe a specific event. Examples: > //This sentence means that you have had the experience of being in France. Maybe you have been there once, or several times.// > //You can add the number of times at the end of the sentence.// > //This sentence means that you have not had the experience of going to France.// > B: No, I **have** not **met** him.
 * I **have been** to France.
 * I **have been** to France three times.
 * I **have** never **been** to France.
 * I think I **have seen** that movie before.
 * He **has** never **traveled** by train.
 * Joan **has studied** two foreign languages.
 * A: **Have** you ever **met** him?

TOPIC 2 Change Over Time
We often use the Present Perfect to talk about change that has happened over a period of time. Examples:
 * You **have grown** since the last time I saw you.
 * The government **has become** more interested in arts education.
 * Japanese **has become** one of the most popular courses at the university since the Asian studies program was established.
 * My English **has** really **improved** since I moved to Australia.

TOPIC 3 Accomplishments
We often use the Present Perfect to list the accomplishments of individuals and humanity. You cannot mention a specific time. Examples:
 * Man **has walked** on the Moon.
 * Our son **has learned** how to read.
 * Doctors **have cured** many deadly diseases.
 * Scientists **have split** the atom.

TOPIC 4 An Uncompleted Action You Are Expecting
We often use the Present Perfect to say that an action which we expected has not happened. Using the Present Perfect suggests that we are still waiting for the action to happen. Examples:
 * James **has not finished** his homework yet.
 * Susan **hasn't mastered** Japanese, but she can communicate.
 * Bill **has** still **not arrived**.
 * The rain **hasn't stopped**.

TOPIC 5 Multiple Actions at Different Times
We also use the Present Perfect to talk about several different actions which have occurred in the past at different times. Present Perfect suggests the process is not complete and more actions are possible. Examples:
 * The army **has attacked** that city five times.
 * I **have had** four quizzes and five tests so far this semester.
 * We **have had** many major problems while working on this project.
 * She **has talked** to several specialists about her problem, but nobody knows why she is sick.

Time Expressions with Present Perfect
When we use the Present Perfect it means that something has happened at some point in our lives before now. Remember, the exact time the action happened is not important.

ometimes, we want to limit the time we are looking in for an experience. We can do this with expressions such as: in the last week, in the last year, this week, this month, so far, up to now, etc.

xamples:
 * **Have** you **been** to Mexico **in the last year**?
 * I **have seen** that movie six times **in the last month**.
 * They **have had** three tests **in the last week**.
 * She graduated from university less than three years ago. She **has worked** for three different companies **so far**.
 * My car **has broken** down three times **this week**.

NOTICE
"Last year" and "in the last year" are very different in meaning. "Last year" means the year before now, and it is considered a specific time which requires [|Simple Past]. "In the last year" means from 365 days ago until now. It is not considered a specific time, so it requires Present Perfect. Examples: > //I went to Mexico in the calendar year before this one.// > //I have been to Mexico at least once at some point between 365 days ago and now.//
 * I **went** to Mexico **last year**.
 * I **have been** to Mexico **in the last year**.

USE 2 Duration From the Past Until Now (Non-Continuous Verbs)
ith [|Non-Continuous Verbs] and non-continuous uses of [|Mixed Verbs], we use the Present Perfect to show that something started in the past and has continued up until now. "For five minutes," "for two weeks," and "since Tuesday" are all durations which can be used with the Present Perfect. Examples: Although the above use of Present Perfect is normally limited to Non-Continuous Verbs and non-continuous uses of Mixed Verbs, the words "live," "work," "teach," and "study" are sometimes used in this way even though they are NOT Non-Continuous Verbs.
 * I **have had** a cold for two weeks.
 * She **has been** in England for six months.
 * Mary **has loved** chocolate since she was a little girl.

ADVERB PLACEMENT
The examples below show the placement for grammar adverbs such as: always, only, never, ever, still, just, etc. Examples:
 * You have **only** seen that movie one time.
 * Have you **only** seen that movie one time?

Reference:http://www.englishpage.com/verbpage/presentperfect.html media type="youtube" key="l2fPHzkBMok" height="390" width="480"media type="youtube" key="ukT7GJcoVOY" height="390" width="640" media type="youtube" key="7S_gLohI4XE" height="390" width="480"media type="youtube" key="ekMDFY96r9A" height="390" width="480"