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NIST-F1, source of the official time of the United States. NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took fewer than four years to test and build, and was developed ...
A few rare variants place noon and midnight at the right and left sides. [9] There is no ambiguity if the 24-hour numbering is used. In the United States, the government and military commonly use 24-hour clocks having noon at the bottom; the variant with noon at the top is far less common. [citation needed]
A world clock is a clock which displays the time for various cities around the world. The display can take various forms: The clock face can incorporate multiple round analogue clocks with moving hands or multiple digital clocks with numeric readouts, with each clock being labelled with the name of a major city or time zone in the world. The ...
NPL-CsF2, Yb+ and Sr+ ion clocks, Sr lattice clock, 4 hydrogen masers [5] [6] National Physical Laboratory; ... El Paso County, Colorado United States [11] WWV
WWVB's Colorado location makes the signal weakest on the U.S. east coast, where urban density also produces considerable interference. In 2009, NIST raised the possibility of adding a second time code transmitter, on the east coast, to improve signal reception there and provide a certain amount of robustness to the overall system should weather or other causes render one transmitter site ...
TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories worldwide. [3] The majority of the clocks involved are caesium clocks; the International System of Units (SI) definition of the second is based on caesium. [6]
WWV Transmitter Building (2002 or earlier) WWV's 15 MHz antenna WWV is a shortwave ("high frequency" or HF) radio station, located near Fort Collins, Colorado.It has broadcast a continuous time signal since 1945, and implements United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, 20, and 25 MHz. [1]
Before the adoption of four standard time zones for the continental United States, many towns and cities set their clocks to noon when the sun passed their local meridian, pre-corrected for the equation of time on the date of observation, to form local mean solar time. Noon occurred at different times but time differences between distant ...