DUT1 (sometimes also written DUT) is a time correction equal to the difference between
Universal Time (
UT1), which is defined by
Earth's rotation
Earth's rotation or Earth's spin is the rotation of planet Earth around its own Rotation around a fixed axis, axis, as well as changes in the orientation (geometry), orientation of the rotation axis in space. Earth rotates eastward, in retrograd ...
, and
Coordinated Universal Time (UTC), which is defined by a network of precision
atomic clocks.
:DUT1 = UT1 − UTC
UTC is maintained via
leap seconds, such that DUT1 remains within the range −0.9 s < DUT1 < +0.9 s. The reason for this correction is partly that the rate of rotation of the Earth is not constant, due to
tidal braking and the redistribution of mass within the Earth, including its oceans and atmosphere, and partly because the
SI second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each ...
(as now used for
UTC) was, when adopted, a little shorter than the current value of the second of mean solar time.
Daily observed values of DUT1 for the past week, and daily forecast values for the coming year, are published by
IERS
The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Pa ...
br>
Bulletin A
Several
time signal services broadcast values of DUT1.
CHU
Chu or CHU may refer to:
Chinese history
* Chu (state) (c. 1030 BC–223 BC), a state during the Zhou dynasty
* Western Chu (206 BC–202 BC), a state founded and ruled by Xiang Yu
* Chu Kingdom (Han dynasty) (201 BC–70 AD), a kingdom of the Ha ...
(Canada),
HLA (South Korea),
MSF (United Kingdom), and
WWV (United States) transmit DUT1 with 0.1 s precision. In Russia,
RWM
RWM is the callsign of a high frequency (shortwave) standard frequency and time signal radio station in Moscow, Russia. It is controlled by All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology, and ope ...
,
RTZ and the longwave
RBU transmit DUT1 with 0.1 s precision and an additional correction dUT1 in 0.02 s increments.
Notes
References
* ITU-R Recommendation TF.460-4: Standard-frequency and time-signal emissions.
International Telecommunication Union.
External links
IERS Bulletins including Bulletin A - latest and past versions, and graphical plots
* Latest version o
Bulletin AIERS Rapid Service/Prediction Center via the US Naval ObservatoryArchived version
available for non-US readers)
* http://scienceworld.wolfram.com/astronomy/Time.html
* https://web.archive.org/web/20161115072453/http://maia.usno.navy.mil/ser7/deltat.data
{{Time measurement and standards
Time scales