SUBROUTINE iau_EQEC06 ( DATE1, DATE2, DR, DD, DL, DB )
*+
*  - - - - - - - - - - -
*   i a u _ E Q E C 0 6
*  - - - - - - - - - - -
*
*  Transformation from ICRS equatorial coordinates to ecliptic
*  coordinates (mean equinox and ecliptic of date) using IAU 2006
*  precession model.
*
*  This routine is part of the International Astronomical Union's
*  SOFA (Standards of Fundamental Astronomy) software collection.
*
*  Status:  support routine.
*
*  Given:
*     DATE1,DATE2  d      TT as a 2-part Julian Date (Note 1)
*     DR,DD        d      ICRS right ascension and declination (radians)
*
*  Returned:
*     DL,DB        d      ecliptic longitude and latitude (radians)
*
*  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
*
*         2450123.7D0        0D0        (JD method)
*          2451545D0      -1421.3D0     (J2000 method)
*         2400000.5D0     50123.2D0     (MJD method)
*         2450123.5D0       0.2D0       (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) No assumptions are made about whether the coordinates represent
*     starlight and embody astrometric effects such as parallax or
*     aberration.
*
*  3) The transformation is approximately that from mean J2000.0 right
*     ascension and declination to ecliptic longitude and latitude (mean
*     equinox and ecliptic of date), with only frame bias (always less
*     than 25 mas) to disturb this classical picture.
*
*  Called:
*     iau_S2C      spherical coordinates to unit vector
*     iau_ECM06    J2000.0 to ecliptic rotation matrix, IAU 2006
*     iau_RXP      product of r-matrix and p-vector
*     iau_C2S      unit vector to spherical coordinates
*     iau_ANP      normalize angle into range 0 to 2pi
*     iau_ANPM     normalize angle into range +/- pi
*
*  This revision:  2016 February 9
*
*  SOFA release 2017-04-20
*
*  Copyright (C) 2017 IAU SOFA Board.  See notes at end.
*
*-----------------------------------------------------------------------

      IMPLICIT NONE

      DOUBLE PRECISION DATE1, DATE2, DR, DD, DL, DB

      DOUBLE PRECISION RM(3,3), V1(3), V2(3), A, B

      DOUBLE PRECISION iau_ANP, iau_ANPM

* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


*  Spherical to Cartesian.
      CALL iau_S2C ( DR, DD, V1 )

*  Rotation matrix, ICRS equatorial to ecliptic.
      CALL iau_ECM06 ( DATE1, DATE2, RM )

*  The transformation from ICRS to ecliptic.
      CALL iau_RXP ( RM, V1, V2 )

*  Cartesian to spherical.
      CALL iau_C2S ( V2, A, B )

*  Express in conventional ranges.
      DL = iau_ANP ( A )
      DB = iau_ANPM ( B )

*  Finished.

*+----------------------------------------------------------------------
*
*  Copyright (C) 2017
*  Standards Of Fundamental Astronomy Board
*  of the International Astronomical Union.
*
*  =====================
*  SOFA Software License
*  =====================
*
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*
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*  CONDITIONS WHICH APPLY TO ITS USE.
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*  1. The Software is owned by the IAU SOFA Board ("SOFA").
*
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*-----------------------------------------------------------------------

      END