What year should your w2 say when filing for the current year?

It should say 2017 for the tax year that is being filed now.

Here’s the IRS blank W2 for 2017 so you can see the current form.
<a rel="nofollow" target="_blank" href="https://www.irs.gov/pub/irs-pdf/fw2_17.pdf">https://www.irs.gov/pub/irs-pdf/fw2_17.pdf</a>