[Grammar] had been

[Maybo]

Your improvement had been spectacular.
Your improvement was spectacular.
What's the difference?

 

[Maybo]

With the first, you need a past time-point up to which the being spectacular had extended,

Your improvement had been spectacular after 1985. Can I say that?

Another question, I don't understand the structure of this sentence, how to use to which?
With the first, you need a past time-point up to which the being spectacular had extended.

 

[Maybo]

I suppose it's possible to come up with a context in which you could say that. It is more natural to use the past perfect for a situation that extends up to a time, not one starting from/at a time.

You need a time-point. The being spectacular extends up to this point.
We join these two sentences, using 'which', a relative pronoun, the antecedent of which is 'a time-point' in the first sentence, now the first clause:
You need a time-point up to which the being spectacular extends.

Your improvement had been spectacular since 1985.
after 3 months, your improvement had been spectacular.
How about these?

 

[Maybo]

No.

Could you give me some examples?

 

[teechar]

Your improvement had been spectacular [STRIKE]since[/STRIKE] until 1985.

Look at the answer given in post #2.

After 3 months, your improvement had been spectacular until it started deteriorating over the course of 2015.

Something like that is possible.

 

[Maybo]

Look at the answer given in post #2.
Something like that is possible.

The course=The period ?