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The Past Perfect Progressive Tense is being defined that an action started in tha past before another action and continued up to that action or particular time. It is clear with "for+time", ex: When kids went out, it had been raining for 2 hours.

But this tense when comes with "since+time" like: They had been playing since morning; how we can realise the second action or particular time which is the end of first action?

please share your knowledge in this regard.

Thanks in advance.
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Hakeemhow we can realise the second action or particular time which is the end of first action?
You show the reference time through context. You need more of a story in which to place the actions. Isolated sentences with a past perfect don't always make sense. They only make sense within a larger story.

Several days ago, on a sunny afternoon, I visited my friend Louise at her home.

I noticed her children playing in the sandbox.

They seemed very focused on building a castle with the sand.

Louise said they had been playing since morning.

CJ
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Thanaks a lot CJ,

Is it the case with the Future Perfect Continuous Tense?

Can you provide such context, a F.P.C tense with SINCE?
HakeemCan you provide such context, a F.P.C tense with SINCE?
That combination is quite rare, but you might say, awkwardly,

By the end of the year, I will have been reading War and Peace since May.

More natural is a for-phrase:

By the end of the year, I will have been reading War and Peace for seven months.

CJ
Bundle of THANKS, I got my answer.
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