Next year I will have been married for 10 years.
Future Perfect is one of the tenses used to express the future. It is not very common but can be helpful to explain some specific situations.
Will + have + past participle I will have done...
When to use:
Future completed actions - to show that an action or situation will be complete before a certain time in the future. We often use by for this:
Duration of actions - to talk about the duration of an action or situation that will continue until a certain time in the future. We often use for for this:
Tip: It is easier to understand Future Perfect if you compare it with Present Perfect:
|A 90 second overview of the future perfect||BBC Learning|