The phoeboscope is presented as a self-sufficient instrument combining time-keeping, meridian-finding, and calendrical functions by detecting solar declination. Designed during WWII as an improvement of the existing sun-compass, its adoption was frustratingly held up in bureaucracy until too late to be useful. It uses a lens to focus sunlight onto a shadow-plate engraved with an analemma, allowing accurate determination of time, meridian, and date anywhere in the world without a watch or almanac.
DIY Sundial Projects,
Dials: Heliochronometer,
Dials: Unusual,
Equation of Time