Could you explain the differences between the two tenses? When should I use present perfect continuous and when should I use past perfect continuous?
"I had been doing before I was young"
"I have been doing"
Could you explain the differences between the two tenses? When should I use present perfect continuous and when should I use past perfect continuous?
"I had been doing before I was young"
"I have been doing"
Present Perfect Continuous is for when an event began in the past but is still going on, like a sitting member of Congress ("I have been representing these people for the past 20 years"); his first term was long ago, but he is still serving today.
Likewise, Past Perfect Continuous is for when something happened in the past, then continued for a while, but then stopped (ie, it's no longer going on at the present time). For example: "He had been serving as Congressman for 20 years before he retired".
These are different from simply Present Perfect and Past Perfect (ie not Continuous) in that they refer to events that happened in the past without the duration of the event being measured, rather than Continuous, where events happened in the past and then continue(d) for some (measured) time. This isn't to say that the measurement must be specific; you can say "I've been doing this for the past while" just as well as "I've been doing this for the past five months".