Sub-Topics Calendars Papers Earliest Clocks History of Clocks (NIST) 3-00 History of Clocks (Weissman) 3-00 History of the Clock (Sterling Infotech Enterprise) Provides a history of the development of the clock. 7-00 Sundial Construction (North American Sundial Society) Provides instructions for completing a sundial, as well as help with the concept of time. 5-00 Timekeeping (Wikipedia.org) Provides information on time, such as leap year, sidereal time, and daylight saving time. Includes high level mathematics. 10-04 Times for Sunrise and Sunset (USA Today) Vedic Timekeeping (Wikipedia.org) Provides the Hindu metrics of time. 10-04 World Clock Time Zones (24TimeZones.com Provides the correct time and date by a map of the world and major city. 05-08 World Clock Time Zones (TijmeGenie.com) Provides the correct time and date by major city. 05-08 World Clock Time Zones (timeanddate.com Provides the correct time and date by major city. 05-08 Worksheets New Clock - World's Most Accurate (BBC News) Describes a new clock that is accurate within one second every 15 billion years. Also provides the definition of a second - "Atomic clock technology enabled scientists in 1967 to define the second as the period equal to 9,192,631,770 cycles of the radiation that corresponds to the transition between two energy levels of the ground state of the caesium-133 atom." 7-01

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