Q:

In graph's axis, can we say "somewhere between year1 and year2"?

Here is a graph I get somewhere in the internet for illustration:

Can I say

Somewhere between 2006 and 2010, first three lines raise significantly

...?
If we mention about lines, I think using somewhere is not wrong. But if we using the legends directly, can I use somewhere or I have to use some times?
I find that we can use somewhere down the road and some times down the road at the same time.

A:

As you are referring to a graph, where the lines are physically drawn on a piece of paper (or on a computer screen or whatever), there is clearly a "where", the place on the graph where the lines begin going up. So "somewhere between 2006 and 2010" is perfectly acceptable and is literally accurate. There is a place on the graph between the place marked 2006 and the place marked 2010, etc.
If you were just talking of this trend generally, without reference to a graph, it would be more correct to say "some time between". But people often do say "somewhere between" in that context. Perhaps they are thinking of a graph or perhaps their language is just getting a little sloppy.
BTW "first three lines" requires an article. It should be "THE first three lines". And we don't say that a trend "raises", we say that it "rises". So the sentence should be, "Somewhere between 2006 and 2010, the first three lines rise significantly."

