Cite related work from same year as defense? Suppose I do the research for my thesis from 2013 to 2016, and do the write-up of the dissertation in 2016.

If during write-up in 2016 I discover new related work (published during 2016), is it eligible to put it into the related work section of my thesis? Or should this related work have already existed in the beginning of the thesis to be part of its related work?
Of course, you should include anything that is relevant regardless of when you started your thesis.

I have even seen dissertations that cite work that is unpublished or still under review.