If you have access to a 3D printer you may be interested in creating your very own digital sundial created by Mojoptix a few years ago. The sundial requires no batteries or electronics and uses the direction of the centre display a digital style readout on the ground. Check out the demonstration video below
“A Sundial displaying the time inside its shadow, with actual digits ! There is a tiny bit of magic inside… No batteries, no motor, no electronics… It’s all just a really super-fancy shadow show. The shape of the sundial has been mathematically designed to only let through the right sunrays at the right time/angle. This allows to display the actual time with sunlit digits inside the sundial’s shadow. The sundial displays time (with actual digits !!) from 10:00 until 16:00, updating every 20 minutes. You can precisely adjust the displayed time simply by rotating the gnomon (the magic box that displays time). So you can even adjust for Daylight Saving Time.”
If you fancy 3D printing your very own digital sundial jump over to the Thingiverse website via the link below. Mojoptix has also provided the 3D files to print the mounting system which can be easily attached to a weighted jam jar.