More commonly called sundials, I recently built this solar powered clock as an educational project to do with my grandchildren.
I became interested in making one after seeing an Instructables post for making sundials from paper. It has a number of different kits with versions for the Northern and Southern hemispheres.
Paper Sundial Kits - credit https://www.instructables.com/Paper-Sundial-Kits/
The author also has a web site here with lots more information on how to design and build different sundials. I tried one with paper but thought my 6 year-old granddaughter might not have the fine motor skills (plus I didn't want her anywhere near a hobby knife). And I didn't have any really sturdy cardstock. So I whipped one up in Fusion 360 and printed it in PLA. Probably not the best thing to set out in the hot sun but it is February in Portland and we don't have sun at the moment, much less hot weather. I made my version with a hinge to set the latitude as opposed to the wedge shaped base in the original.