src/Marando/IAU/iauEe00.php
public static function Ee00($date1, $date2, $epsa, $dpsi) {
    $ee;

    /* Equation of the equinoxes. */
    $ee = $dpsi * cos($epsa) + IAU::Eect00($date1, $date2);

    return $ee;
  }
public static function Ee00($date1, $date2, $epsa, $dpsi) {
    $ee;

    /* Equation of the equinoxes. */
    $ee = $dpsi * cos($epsa) + IAU::Eect00($date1, $date2);

    return $ee;
  }
public static function Ee00 ( $ date1 , $ date2 , $ epsa , $ dpsi ) { $ ee ; /* Equation of the equinoxes. */ $ ee = $ dpsi * cos ( $ epsa ) + IAU :: Eect00 ( $ date1 , $ date2 ) ; return $ ee ; }
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The equation of the equinoxes, compatible with IAU 2000 resolutions,
given the nutation in longitude and the mean obliquity.

This function is part of the International Astronomical Union's
SOFA (Standards Of Fundamental Astronomy) software collection.

Status:  canonical model.

Given:
date1,date2  double    TT as a 2-part Julian Date (Note 1)
epsa         double    mean obliquity (Note 2)
dpsi         double    nutation in longitude (Note 3)

Returned (function value):
double    equation of the equinoxes (Note 4)

Notes:

1) The TT date date1+date2 is a Julian Date, apportioned in any
convenient way between the two arguments.  For example,
JD(TT)=2450123.7 could be expressed in any of these ways,
among others:

date1          date2

2450123.7           0.0       (JD method)
2451545.0       -1421.3       (J2000 method)
2400000.5       50123.2       (MJD method)
2450123.5           0.2       (date & time method)

The JD method is the most natural and convenient to use in
cases where the loss of several decimal digits of resolution
is acceptable.  The J2000 method is best matched to the way
the argument is handled internally and will deliver the
optimum resolution.  The MJD method and the date & time methods
are both good compromises between resolution and convenience.

2) The obliquity, in radians, is mean of date.

3) The result, which is in radians, operates in the following sense:

Greenwich apparent ST = GMST + equation of the equinoxes

4) The result is compatible with the IAU 2000 resolutions.  For
further details, see IERS Conventions 2003 and Capitaine et al.
(2002).

Called:
iauEect00    equation of the equinoxes complementary terms

References:

Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
implement the IAU 2000 definition of UT1", Astronomy &
Astrophysics, 406, 1135-1149 (2003)

McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
IERS Technical Note No. 32, BKG (2004)

This revision:  2008 May 16

SOFA release 2015-02-09

Copyright (C) 2015 IAU SOFA Board.  See notes at end.
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