When using the present perfect tense, you need an auxiliary verb that helps your main verb to function. In the perfect tenses, the verb (to) have is always the auxiliary verb. In the present perfect tense, the main verb is in the past participle form. This is not difficult for regular past tense verbs. For regular verbs, the past participle form of the verb is the same as the past tense verb, so you just add -ed! But irregular verbs are different and the only way to learn the past participle form is to learn them individually. Past simple or present perfect tense? To answer this question you need to think about time. Finished time and unfinished time. Think about ‘last week’. That’s a good example of finished time. Last week is finished, it’s over. Yesterday, last week, last month, last year, 1991 - these are all examples of finished time… Time that is complete. What about ‘this week’? Is this week finished? No! Not yet. That is an example of unfinished time. There’s still more of this week to come. It’s not finished yet. When you are talking about a time period that has finished, use the past simple. When you are talking about a time period that is unfinished… Like today, this week, this month, this year, use the present perfect. Watch this lesson to learn when to use the present perfect and when to use the past simple tense.