It's been

[ShadeWe]

Actually I know what it's been means, but I can't explain why this structure is used somewhere. Consequently, I may not know how to use this structure properly, I think.

It's been in use since the sixth century.

Q: Why isn't the present perfect continuous used here? Are the Present Perfect and the Present Perfect Continuous interchangeable in some cases or something?

There was an event that affected the country and someone says:
It's been so great for our country.

Q: Why can't I just use was instead of has?

I can only explain why this structure is used with time indicators like:

It's been so long
It's been a while
It's been a year

a particular amount of time has passed since a particular event.

Can someone give me some examples and the explanations of examples? (Under explanations I mean why this structure is used) Maybe I will understand.:roll:

 

[jutfrank]

It's been in use since the sixth century.

Q: Why isn't the present perfect continuous used here? Are the Present Perfect and the Present Perfect Continuous interchangeable in some cases or something?

When the verb stands for a state (e.g. to be), you can just use present perfect simple, where with other, non-stative verbs you would use present perfect continuous.

 

[andrewg927]

"It's been in use since the sixth century" means it started in the sixth century but it is still in use now.
"It's been so great for our country" means the event was in the past but the effects of it can still be felt in the present.
"It was so great for our country" is correct but it means the effects of the event are no longer felt in the present.

You mentioned present perfect continuous, what is your suggestion for the sentence above?

 

[Raymott]

It's been so great for our country.

Q: Why can't I just use was instead of has?

In questions like this it would be better to actually use the word you're asking about. You haven't used 'has'.
Eg. "It has been so great for our country." You need to be aware that contractions can mean more than one thing. For example, in "It's being uncooperative", the "It's" stands for "It is".
It's a small point, but an important one.