Present continuous and present perfect continuous

Incorrect: I am working for the last two hours.

Correct: I have been working for the last two hours.

Incorrect: He is working in this office for three years now.

Correct: He has been working in this office for three years now.

Incorrect: She is working since morning.

Correct: She has been working since morning.

Here the error lies in using the present continuous instead of present perfect continuous. The present continuous tense is used to talk about an action that is going on at the time of speaking. Here the emphasis is simply on the continuity of the action. The present perfect continuous is used to talk about an action which started in the past, has gone on till the present and is still continuing. In the sentence I have been working for two hours, I started working two hours ago, worked without stopping for two hours and am still working. The present perfect continuous tense is used to show emphasis on the duration and continuity. The adverbs since and for are very common in these sentences.

Present perfect and simple past

Incorrect: I have written to him yesterday.

Correct: I wrote to him yesterday.

Incorrect: We have visited them last week.

Correct: We visited them last week.

Incorrect: He has died two years ago.

Correct: He died two years ago.

Here the error lies in using the present perfect instead of simple past.

The present perfect tense is a present tense. You cannot use an adverb of past time with a present tense. If you have to mention a point of past time, use the simple past.

I saw him last week. (NOT I have seen him last week.)

Present tense and future tense

Incorrect: I shall call you when the dinner will be ready.

Correct: I shall call you when the dinner is ready.

Incorrect: They will come if you will invite them.

Correct: They will come if you invite them.

When the verb in the main clause is in the future tense, the verb in the subordinate clause should be in the present and not in the future.

Simple past and past perfect

Incorrect: I had been to Bombay recently.

Correct: I went to Bombay recently.

Incorrect: I had spoken to him last night.

Correct: I spoke to him last night.

Here the error lies in using the past perfect tense instead of simple past tense. The past perfect tense indicates that an action completed at some point in the past before another past action commenced.

Credit goes to : ervaughn
Source : Indogamers English World