Editing Clock (section)

===Sundials===

{{Main|Sundial}}

[[File:Garden sundial MN 2007.JPG|thumb|right|Simple horizontal sundial]]

The apparent position of the Sun in the sky changes over the course of each day, reflecting the rotation of the Earth. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A sundial shows the time by displaying the position of a shadow on a (usually) flat surface that has markings that correspond to the hours.<ref>{{cite web|title=How Sundials Work|date=November 7, 2013|url=http://sundialsoc.org.uk/discussions/how-do-sundials-work/|publisher=The British Sundial Society|access-date=10 November 2014|archive-date=November 10, 2014|archive-url=https://web.archive.org/web/20141110144533/http://sundialsoc.org.uk/discussions/how-do-sundials-work/|url-status=live}}</ref> Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in [[ancient times]].<ref>{{cite web|title=Ancient Sundials|url=http://sundials.org/index.php/all-things-sundial/ancient-sundials|publisher=North American Sundial Society|access-date=10 November 2014|archive-date=November 10, 2014|archive-url=https://web.archive.org/web/20141110142221/http://sundials.org/index.php/all-things-sundial/ancient-sundials|url-status=live}}</ref> With knowledge of latitude, a well-constructed sundial can measure local [[solar time]] with reasonable accuracy, within a minute or two. Sundials continued to be used to monitor the performance of clocks until the 1830s, when the use of the telegraph and trains standardized time and time zones between cities.<ref>{{Cite book |last=Lankford |first=John |url=https://books.google.com/books?id=Xev7zOrwLHgC&pg=PA502 |title=History of Astronomy: An Encyclopedia |date=1997 |publisher=Taylor & Francis |isbn=978-0-8153-0322-0 |language=en}}</ref>