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"Libraries today are different from those in the 1800s. For example, the contents of libraries have changed greatly through the years."

I can't understand why it uses present perfect. I think with "Through the years" (in 1800s) it should use simple past. Thank you in advance:)

P. E. Dant Reinstate Monica
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Beth
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1 Answers1

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The sentence is not about changes which happened in the 19th century but about changes which occurred in the years since the 19th century, as a result of which we have very different libraries today.

This is the core use of the present perfect: to mention a past eventuality ("contents changed") as the source from which a present state ("libraries today") arose.

For more about this see What is the perfect, and how should I use it?, especially §§ 3.1 Grammatical meaning, 3.2 Pragmatic meaning and 4. When and how should I use the perfect?.

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StoneyB on hiatus
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  • I got it roughly. But how could we know the answer without guessing the meaning? I mean, Grammatically , using simple past is right or not? Thank you so much – Beth Aug 24 '16 at 04:46
  • @Beth It's grammatical, but it's a different focus. When you use the simple past, you are focused on the past; when you use the present perfect you are talking about the past in order to describe the present. – StoneyB on hiatus Aug 24 '16 at 10:27