It's not surprising that 2017 was a day shorter than 2016 because of a leap day. But 2016 also had a leap second in it.
What's fascinating to me about that is that good clock design can handle the insertion of a leap second. I came across this project by @Michel which has a video of a GPS clock ticking past :59 to :60 before cranking over to zero at the start of 2017. I figured it's a fun way to close out the year:
The project is using the ZDA NMEA sentence as input and displaying it on the screen. Very geeky, and very cool!