This is a Moon Phase Clock.

Being broke 2 days before Mother's Day, I knew I needed something for the wife, but didn't have any cash.

Scrolling through thingiverse, I though a maybe some glowing lithopane thing would be nice, when I stumbled upon benjaminedwardmorgan's Moon Lithopane...

And it hit me. My wiccan wife often would miss the full moon - lucky for me, I am not a frog yet - and since I make all kinds of LED clocks, I decided to make for her, a Lunar Phase Clock.

This is that clock.