Quote Originally Posted by Raymott View Post
"Over" and "for" is not the issue. Nor is days/weeks/centuries... The same rule applies.
Now, in post #3, you said "
I already know this one "The previous century" depends on what is given as the base century."
But then you make the illogical leap to assuming
So you mean here just "
over the previous few days"is right?"

No, I meant "Only 'over the last few days' is right". Why should "the previous few days" not depend on the base day just the same as "the previous century"? (It does). "Previous" requires mention of a base time. For "last", the base time is now.
There should be no more explaining necessary if you read the thread carefully again.

Thank you all. I got it clearly well.Because we don't have such clear-cut reason for their difference in my mother tongue, that's why I got kind of mixed-up at fist. Sorry for stretching the thread. However all your explanations were of great help to me.