Compare 'Will have + past participle ' with other perfect forms.

Compare ' Will have + past participle 'with other perfect forms. This is a short comparison of ' Present Perfect, Future Perfect and Past Perfect ' Examples:

• They have been married for 20 years.( present perfect - shows the present position. We don't say , ' They are married for..............))
• By the end of December next year they will have been married for 21 years. ( future perfect - shows the future position. We don't say, ' They will be married for........))
• When their first child was born, they had been married for three years. ( past perfect - shows the past position. We don't say , ' They were married for........))