A shadow pole can be used to identify specific days in latitudes within the range just beyond the Tropic of Cancer to the Arctic Circle and beyond the Tropic of Capricorn to the Antarctic Circle. Prehistoric cultures could have employed this simple gnomon as a seasonal calendar for significant days (solstices, equinoxes, feast days, etc.) that would have been marked on the pole. Each marked pole would be specific to its latitude.
This Demonstration is set to provide measurements for poles 100 units tall; for practical purposes the units might as well be inches. At the top of the pole, an overhanging member, extending toward the Sun, creates a shadow that travels along the pole from day to day.