UTCUT1 Subroutine

  1. astro_module.f90
  2. astro_module
  3. UTCUT1

public subroutine UTCUT1(utc1, utc2, dut1, ut11, ut12, j)

Time scale transformation: Coordinated Universal Time, UTC, to Universal Time, UT1.

Status: canonical.

Notes

  1. UTC1+UTC2 is quasi Julian Date (see Note 2), apportioned in any convenient way between the two arguments, for example where UTC1 is the Julian Day Number and UTC2 is the fraction of a day.

  2. JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present routine is that the JD day represents UTC days whether the length is 86399, 86400 or 86401 SI seconds.

  3. The warning status "dubious year" flags UTCs that predate the introduction of the time scale or that are too far in the future to be trusted. See DAT for further details.

  4. The routine DTF2D converts from calendar date and time of day into 2-part Julian Date, and in the case of UTC implements the leap-second-ambiguity convention described above.

  5. Delta UT1 can be obtained from tabulations provided by the International Earth Rotation and Reference Systems Service. It is the caller's responsibility to supply a DUT1 argument containing the UT1-UTC value that matches the given UTC.

  6. The returned UT11,UT12 are such that their sum is the UT1 Julian Date.

References

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

  • Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992)

History

  • IAU SOFA revision: 2013 August 12
  • 11/21/2019: for astro_module, renamed the local variable 'dat' to 'd' so as not to conflict with the subroutine DAT.

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in) :: utc1

UTC as a 2-part quasi Julian Date (Notes 1-4)
real(kind=wp), intent(in) :: utc2

UTC as a 2-part quasi Julian Date (Notes 1-4)
real(kind=wp), intent(in) :: dut1

Delta UT1 = UT1-UTC in seconds (Note 5)
real(kind=wp), intent(out) :: ut11

UT1 as a 2-part Julian Date (Note 6)
real(kind=wp), intent(out) :: ut12

UT1 as a 2-part Julian Date (Note 6)
integer, intent(out) :: j
  • +1 = dubious year (Note 3)
  • 0 = OK
  • -1 = unacceptable date

Calls

proc~~utcut1~~CallsGraph proc~utcut1 UTCUT1 proc~jd2cal JD2CAL proc~utcut1->proc~jd2cal proc~dat DAT proc~utcut1->proc~dat proc~utctai UTCTAI proc~utcut1->proc~utctai proc~taiut1 TAIUT1 proc~utcut1->proc~taiut1 proc~cal2jd CAL2JD proc~dat->proc~cal2jd proc~utctai->proc~jd2cal proc~utctai->proc~dat proc~utctai->proc~cal2jd

Called by

proc~~utcut1~~CalledByGraph proc~utcut1 UTCUT1 proc~apco13 APCO13 proc~apco13->proc~utcut1 proc~apio13 APIO13 proc~apio13->proc~utcut1 proc~atco13 ATCO13 proc~atco13->proc~apco13 proc~atoi13 ATOI13 proc~atoi13->proc~apio13 proc~atio13 ATIO13 proc~atio13->proc~apio13 proc~atoc13 ATOC13 proc~atoc13->proc~apco13

Contents

Source Code

UTCUT1

Source Code

    subroutine UTCUT1 ( utc1, utc2, dut1, ut11, ut12, j )

    implicit none

    real(wp),intent(in) :: utc1 !! UTC as a 2-part quasi Julian Date (Notes 1-4)
    real(wp),intent(in) :: utc2 !! UTC as a 2-part quasi Julian Date (Notes 1-4)
    real(wp),intent(in) :: dut1 !! Delta UT1 = UT1-UTC in seconds (Note 5)
    real(wp),intent(out) :: ut11 !! UT1 as a 2-part Julian Date (Note 6)
    real(wp),intent(out) :: ut12 !! UT1 as a 2-part Julian Date (Note 6)
    integer,intent(out) :: j !! status:
                             !! * +1 = dubious year (Note 3)
                             !! * 0 = OK
                             !! * -1 = unacceptable date

    integer :: iy, im, id, js, jw
    real(wp) :: w, d, dta, tai1, tai2

    !  Look up TAI-UTC.
    call JD2CAL ( utc1, utc2, iy, im, id, w, js )
    if ( js==0 ) then

      call DAT ( iy, im, id, 0.0_wp, d, js )
      if ( js>=0 ) then

        !  Form UT1-TAI.
        dta = dut1 - d

        !  UTC to TAI to UT1.
        call UTCTAI ( utc1, utc2, tai1, tai2, jw )
        if ( jw<0 ) then
          js = jw
        else
          call TAIUT1 ( tai1, tai2, dta, ut11, ut12, jw )
        end if

      end if

    end if

    !  Return the status.
    j = js

    end subroutine UTCUT1