The Sun does not return to the same position in the sky every 24 hours. At local noon, for example, the Sun will appear higher in the sky as we move from winter to summer solstice. In addition, and perhaps more surprisingly, solar days (the roughly 24 hours between subsequent local noons) vary in length, causing the Sun to be east or west of its location 24 hours prior. Over a year, this variation traces out a figure 8, known as an analemma, as shown in Fig.1. It can also be seen in the sundial in Fig. 2, where the gnomon incorporates the analemma to produce an accurate reading of local time.