CAL2JD Subroutine

  1. astro_module.f90
  2. astro_module
  3. CAL2JD

public subroutine CAL2JD(iy, im, id, djm0, djm, j)

Gregorian Calendar to Julian Date.

Status: support routine.

Notes

  1. The algorithm used is valid from -4800 March 1, but this implementation rejects dates before -4799 January 1.

  2. The Julian Date is returned in two pieces, in the usual SOFA manner, which is designed to preserve time resolution. The Julian Date is available as a single number by adding DJM0 and DJM.

  3. In early eras the conversion is from the "Proleptic Gregorian Calendar"; no account is taken of the date(s) of adoption of the Gregorian Calendar, nor is the AD/BC numbering convention observed.

Reference

  • Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 12.92 (p604).

History

  • IAU SOFA revision: 2014 November 7

Arguments

TypeIntentOptionalAttributesName
integer, intent(in) :: iy

year in Gregorian calendar (Note 1)
integer, intent(in) :: im

month in Gregorian calendar (Note 1)
integer, intent(in) :: id

day in Gregorian calendar (Note 1)
real(kind=wp), intent(out) :: djm0

MJD zero-point: always 2400000.5
real(kind=wp), intent(out) :: djm

Modified Julian Date for 0 hrs
integer, intent(out) :: j
  • 0 = OK
  • -1 = bad year (Note 3: JD not computed)
  • -2 = bad month (JD not computed)
  • -3 = bad day (JD computed)

Called by

proc~~cal2jd~~CalledByGraph proc~cal2jd CAL2JD proc~dat DAT proc~dat->proc~cal2jd proc~dtf2d DTF2D proc~dtf2d->proc~cal2jd proc~dtf2d->proc~dat proc~utctai UTCTAI proc~utctai->proc~cal2jd proc~utctai->proc~dat proc~ut1utc UT1UTC proc~ut1utc->proc~cal2jd proc~ut1utc->proc~dat proc~utcut1 UTCUT1 proc~utcut1->proc~dat proc~utcut1->proc~utctai proc~taiutc TAIUTC proc~taiutc->proc~utctai proc~apco13 APCO13 proc~apco13->proc~utctai proc~apco13->proc~utcut1 proc~apio13 APIO13 proc~apio13->proc~utctai proc~apio13->proc~utcut1 proc~d2dtf D2DTF proc~d2dtf->proc~dat 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

CAL2JD

Source Code

    subroutine CAL2JD ( iy, im, id, djm0, djm, j )

    implicit none

    integer,intent(in) :: iy !! year in Gregorian calendar (Note 1)
    integer,intent(in) :: im !! month in Gregorian calendar (Note 1)
    integer,intent(in) :: id !! day in Gregorian calendar (Note 1)
    real(wp),intent(out) :: djm0 !! MJD zero-point: always 2400000.5
    real(wp),intent(out) :: djm !! Modified Julian Date for 0 hrs
    integer,intent(out) :: j !! status:
                             !! *  0 = OK
                             !! * -1 = bad year   (Note 3: JD not computed)
                             !! * -2 = bad month  (JD not computed)
                             !! * -3 = bad day    (JD computed)

    integer :: ndays, my, iypmy

    !  Earliest year allowed (4800BC)
    integer,parameter :: iymin = -4799

    !  Month lengths in days
    integer,dimension(12),parameter :: mtab = [31,28,31,30,31,30,31,31,30,31,30,31]

    !  Preset status.
    j = 0

    !  Validate year.
    if ( iy<iymin ) then
       j = -1
    else

       !  Validate month.
       if ( im>=1 .and. im<=12 ) then

          !  Days in current month.
          ndays = mtab(im)

          !  Allow for leap year.
          if ( im == 2 ) then
             if ( mod(iy,4) == 0 ) ndays = 29
             if ( mod(iy,100)==0 .and. &
                  mod(iy,400)/=0 ) ndays = 28
          end if

          !  Validate day.
          if ( id<1 .or. id>ndays ) j = -3

          !  Result.
          my = ( im - 14 ) / 12
          iypmy = iy + my
          djm0 = 2400000.5_wp
          djm = real( ( 1461 * ( iypmy + 4800 ) ) / 4 &
                    + (  367 * ( im-2 - 12*my ) ) / 12 &
                    - (    3 * ( ( iypmy + 4900 ) / 100 ) ) / 4 &
                    + id - 2432076, wp)

          !  Bad month
       else
          j = -2
       end if
    end if

    end subroutine CAL2JD