![NIST maintains two major time scales. The core scale, AT1, is a weighted average of atomic clocks. The most-used output is the second time scale, UTC(NIST). UTC (NIST) is a real-time realization of the international standard, Coordinated Universal Time (U NIST maintains two major time scales. The core scale, AT1, is a weighted average of atomic clocks. The most-used output is the second time scale, UTC(NIST). UTC (NIST) is a real-time realization of the international standard, Coordinated Universal Time (U](../sites/default/files/styles/full_width_image_700x400max/public/media/images/2015/leapsecond.jpg%3Fitok=j2xXHF3x)
leapsecond.jpg
![NIST maintains two major time scales. The core scale, AT1, is a weighted average of atomic clocks. The most-used output is the second time scale, UTC(NIST). UTC (NIST) is a real-time realization of the international standard, Coordinated Universal Time (U NIST maintains two major time scales. The core scale, AT1, is a weighted average of atomic clocks. The most-used output is the second time scale, UTC(NIST). UTC (NIST) is a real-time realization of the international standard, Coordinated Universal Time (U](../sites/default/files/styles/full_width_image_700x400max/public/media/images/2015/leapsecond.jpg%3Fitok=j2xXHF3x)
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