[has/have + past participle]

The Present Perfect is used to express:
 

1. an action which started in the past and continues up to the present.
   • They have been married for twenty years.
   • How long have you known each other?

2. an action which happened at an unstated time in the past. 

The Present Perfect is used with the following time expressions:

  • just, lately, never, ever, yet, since, for, already