For thousands of years, people have built so-called calendar buildings: buildings that served as sundials for measuring time or were used for astronomical calculations. The most famous examples include the Pyramids of Giza, the Megalithic Temples of Malta, the Solarium Augusti on Rome's Campus Martius, and the ancient observatories in Korea, Baghdad, Cairo, and Samarkand. The oldest known archaeo-astronomical device dates back to around 6000 BCE and was discovered only some twenty years ago at Nabta Playa in Egypt.

The German photographer Hans Pieler (1951-2012) dedicated himself comprehensively to these calendar buildings. In a wide-ranging photographic project spanning fifteen years, Pieler traveled the world in the search for such sites, studied them, and recorded many of them in striking photographs. His interest was focused both on the architecture and its particular coding through the respective culture as well as on the theory of photography, the allegorical image of the time. Due to Pieler's premature death in 2012, the fascinating project remained unfinished and unpublished. This book for the first time features a selection of some one hundred of the best shots from the artist's estate. Complemented by illuminating essays, they form a unique photographic study of these architectures and their meaning and purpose as a reflection of time in stone.