Normally when one mentions a human sundial, we think of an analemmatic dial carefully painted on the ground with a himan gnoman standing carefully on a date in the central walkway.  But you can design a sundial that works for a day or two by just having a central platform, standing on it to become a gnomon, and letting your shadow fall on marked hours drawn on the ground below.  But would you stand there all day?  NASA presented their Astronomical Picture of the Day showing that "on July 19th, the Astronomy Group of students in the Progymnasium Rosenfeld created a human sundial, each participant patiently playing the role of a gnomon for 10 minutes. In this timelapse video of their temporal voyage of discovery, one image was taken every 20 seconds from 8 amuntil4 pm Central European Summer Time. Drawn on the ground are the dial hour marks calculated to show the local time for that specific date. Behind, the tower clock offers a time check... The group plans a repetition of this performance next winter to compare the length of the day and the altitude of the sun."

Video by permission of Astronomie-AG, Progymnasium Rosenfeld, Till Credner,