It will depend on when you were paid for the work.  If you worked the last two weeks of 2016 but your payday fell in Jan of 2017, then whatever was paid in Jan will appear on a 2017 W-2 and you'll report it next year on the 2017 tax return.

If a portion of those last two weeks' wages were paid to you by Dec 31, then that money will be included in the 2016 W-2 and you'll include it on the 2016 return.  Your employer will know the requirements and what to include in a particular year's W-2 form.