I just came across this question:
This tree (be) _____ planted by the settlers who (found) _____ our city over four hundred years ago.
I think "over four hundred years ago" is an unspecified time. My answer was that the two gaps require present perfect. So I was a little surprised with the answer that both of them require simple past. Why is this the case?
Best Answer
A specified past time means that you may not use the present perfect, but that does not imply that an unspecified past time requires that you must use the present perfect.
The present perfect is only used when the past event it describes is in some sense still 'present'. This is a very hard matter to define abstractly -linguists have been struggling with it for generations, and there is still no consensus- but in any given case it's pretty easy for a native speaker to identify. The tree is still here, and the city is still here, but the planting and the founding were "over and done with" long ago.
In any case, over four hundred years ago is "specific" enough to prohibit using the present perfect. "Four hundred years ago" means "a specific point located somewhere around there" - that is, a specific point which definitely does not lie in a timeframe which includes the present.
Consequently, you must use the simple past: