It looks professional, current and that you care, when you take care of the little details on your website.
Several years ago I was 3 moths late before I remembered to change the date on one of my websites.
I spotted a copyright date that was over 2 years behind on a very popular website not too long ago. It just immediately makes you wonder about security and the website owner's current attention and involvement in the site.
It is not as popular anymore but I still like to also keep the beginning date on my authority site. (eg: Copyright © 2003 - 2019)
Lets have a great year!