What year w2 do i use to file taxes this year

To file your 2017 return you would use 2017 W-2s issued by your employer(s).

What year earnings are on 2017 W2's?

2017 of course.  You need to report it the year it is for.  Your employer sends you the W2 by the end of January for the prior year.  If you already filed a 2017 return you need to amend it to add a W2 to it.

Why are you asking?

Oh, are you confused by the first question posted here?  This is a new forum layout. Some posts that have June 2019 dates are really older posts from the old forum that got moved over. So they might be for prior years and not current info. When they migrated over the dates got changed to June 2019. And the screen shots got deleted.