Module: deltat

Computation of an estimate of Delta_T, for astronomical computations with calendars. Delta_T is defined in this way: UTC = TT - Delta_T, where UTC (formerly GMT) is the master time of all our clocks. TT is Terrestrial Time, a uniform time scale defined independently from any Earth movements. Delta_T is erratic and difficult to compute, however, the general trend of Delta_T is due to the braking of the Earth's daily revolution. This estimate of Deltta_T in seconds from the year expressed in Common Era is a quadratic function of the year. The computation of the long-term Delta_T is after Morrison and Stephenson 2021. In this version, the estimated Delta_T is smoothed over time. The result is rounded to the nearest second.
Version:
  • M2021-03-11
Author:
  • Louis A. de Fouquières https://github.com/Louis-Aime
License:
  • MIT 2016-2022
Source:

Methods

(static) getDeltaT(theDate) → {number}

Compute an estimate of Delta T, defined as: UTC = TT - Delta T. The estimate is only the quadratic part of Delta T.
Parameters:
Name Type Description
theDate Date date where Delta T is estimated (estimation is per exact date, not per year).
Source:
Returns:
Delta T, unit is milliseconds, result reflects an integer signed number of seconds.
Type
number