Hello....
Sometimes I find in grammar books that "ago" can be used only with Past tense, not with Past Perfect tense.
Thus, "He did it 5 years ago" is correct, and "He had done it 5 years ago" is wrong.
So, it has to be "He had done it 5 years before".
But often I find the cases where "ago" is used with Past Perfect tenses.
Such examples are as belows:
https://www.google.co.kr/search?num=20&newwindow=1&ei=mB_TW5vDCoGa8wXynoKIAQ&q=%22+had+died+ +years+ago+%22&oq=%22+had+died++years+ago+%22&gs_l=psy-ab.12...0.0.0.2561521.0.0.0.0.0.0.0.0..0.0....0...1c..64.psy-ab..0.0.0....0.9clHoPxCQD4
https://www.google.co.kr/search?num=20&newwindow=1&ei=mynTW8moNYGJ8wWj1ZmICQ&q=%22+had+done+ +years+ago+%22&oq=%22+had+done++years+ago+%22&gs_l=psy-ab.3...22216.23805.0.24989.8.8.0.0.0.0.204.898.0j6j1.7.0....0...1c.1.64.psy-ab..1.1.106...0i8i13i30k1.0.7DFhOM9dmKg
I guess that "ago" can be used with Past Perfect tense and that in this case the time starts from the present, not from a time point in the past.
A. He had done it 5 years ago.
B. He had done it 5 years before.
So, I presume that both A and B are correct but, in A, 5 years starts from the present, while in B, 5 years starts from a point in the past.
Some advice would be greatly appreciated.
" That is not incorrect.
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You may use the past perfect with "ago." That is not incorrect.
The 'temporal deictic' expression "ago" can be used with the past perfect:
She realised that Ed had left at least a week ago.
She claimed she had seen Ed ten years ago.
These would normally be interpreted at face value as "at least a week / ten years before the time of the utterance", (i.e. it measures "at least a week / ten years" backwards from