int iauDtf2d(const char *scale, int iy, int im, int id,
int ihr, int imn, double sec, double *d1, double *d2)
/*
** - - - - - - - - -
** i a u D t f 2 d
** - - - - - - - - -
**
** Encode date and time fields into 2-part Julian Date (or in the case
** of UTC a quasi-JD form that includes special provision for leap
** seconds).
**
** This function is part of the International Astronomical Union's
** SOFA (Standards of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** scale char[] time scale ID (Note 1)
** iy,im,id int year, month, day in Gregorian calendar (Note 2)
** ihr,imn int hour, minute
** sec double seconds
**
** Returned:
** d1,d2 double 2-part Julian Date (Notes 3,4)
**
** Returned (function value):
** int status: +3 = both of next two
** +2 = time is after end of day (Note 5)
** +1 = dubious year (Note 6)
** 0 = OK
** -1 = bad year
** -2 = bad month
** -3 = bad day
** -4 = bad hour
** -5 = bad minute
** -6 = bad second (<0)
**
** Notes:
**
** 1) scale identifies the time scale. Only the value "UTC" (in upper
** case) is significant, and enables handling of leap seconds (see
** Note 4).
**
** 2) For calendar conventions and limitations, see iauCal2jd.
**
** 3) The sum of the results, d1+d2, is Julian Date, where normally d1
** is the Julian Day Number and d2 is the fraction of a day. In the
** case of UTC, where the use of JD is problematical, special
** conventions apply: see the next note.
**
** 4) JD cannot unambiguously represent UTC during a leap second unless
** special measures are taken. The SOFA internal convention is that
** the quasi-JD day represents UTC days whether the length is 86399,
** 86400 or 86401 SI seconds. In the 1960-1972 era there were
** smaller jumps (in either direction) each time the linear UTC(TAI)
** expression was changed, and these "mini-leaps" are also included
** in the SOFA convention.
**
** 5) The warning status "time is after end of day" usually means that
** the sec argument is greater than 60.0. However, in a day ending
** in a leap second the limit changes to 61.0 (or 59.0 in the case
** of a negative leap second).
**
** 6) 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 iauDat for further details.
**
** 7) Only in the case of continuous and regular time scales (TAI, TT,
** TCG, TCB and TDB) is the result d1+d2 a Julian Date, strictly
** speaking. In the other cases (UT1 and UTC) the result must be
** used with circumspection; in particular the difference between
** two such results cannot be interpreted as a precise time
** interval.
**
** Called:
** iauCal2jd Gregorian calendar to JD
** iauDat delta(AT) = TAI-UTC
** iauJd2cal JD to Gregorian calendar
**
** This revision: 2013 July 26
**
** SOFA release 2015-02-09
**
** Copyright (C) 2015 IAU SOFA Board. See notes at end.
*/
{
int js, iy2, im2, id2;
double dj, w, day, seclim, dat0, dat12, dat24, dleap, time;
/* Today's Julian Day Number. */
js = iauCal2jd(iy, im, id, &dj, &w);
if ( js ) return js;
dj += w;
/* Day length and final minute length in seconds (provisional). */
day = DAYSEC;
seclim = 60.0;
/* Deal with the UTC leap second case. */
if ( ! strcmp(scale,"UTC") ) {
/* TAI-UTC at 0h today. */
js = iauDat(iy, im, id, 0.0, &dat0);
if ( js < 0 ) return js;
/* TAI-UTC at 12h today (to detect drift). */
js = iauDat(iy, im, id, 0.5, &dat12);
if ( js < 0 ) return js;
/* TAI-UTC at 0h tomorrow (to detect jumps). */
js = iauJd2cal ( dj, 1.5, &iy2, &im2, &id2, &w);
if ( js ) return js;
js = iauDat(iy2, im2, id2, 0.0, &dat24);
if ( js < 0 ) return js;
/* Any sudden change in TAI-UTC between today and tomorrow. */
dleap = dat24 - (2.0*dat12 - dat0);
/* If leap second day, correct the day and final minute lengths. */
day += dleap;
if ( ihr == 23 && imn == 59 ) seclim += dleap;
/* End of UTC-specific actions. */
}
/* Validate the time. */
if ( ihr >= 0 && ihr <= 23 ) {
if ( imn >= 0 && imn <= 59 ) {
if ( sec >= 0 ) {
if ( sec >= seclim ) {
js += 2;
}
} else {
js = -6;
}
} else {
js = -5;
}
} else {
js = -4;
}
if ( js < 0 ) return js;
/* The time in days. */
time = ( 60.0 * ( (double) ( 60 * ihr + imn ) ) + sec ) / day;
/* Return the date and time. */
*d1 = dj;
*d2 = time;
/* Status. */
return js;
/*----------------------------------------------------------------------
**
** Copyright (C) 2015
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
** include the prefix "iau" or "sofa" or trivial modifications
** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
** not be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** e) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have
** granted a further right to modify the source code of your
** derived work.
**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or
** by inappropriate modification.
**
** 5. The SOFA software is provided "as is" and SOFA makes no warranty
** as to its use or performance. SOFA does not and cannot warrant
** the performance or results which the user may obtain by using the
** SOFA software. SOFA makes no warranties, express or implied, as
** to non-infringement of third party rights, merchantability, or
** fitness for any particular purpose. In no event will SOFA be
** liable to the user for any consequential, incidental, or special
** damages, including any lost profits or lost savings, even if a
** SOFA representative has been advised of such damages, or for any
** claim by any third party.
**
** 6. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: [email protected]
** By post: IAU SOFA Center
** HM Nautical Almanac Office
** UK Hydrographic Office
** Admiralty Way, Taunton
** Somerset, TA1 2DN
** United Kingdom
**
**--------------------------------------------------------------------*/
}
int iauUt1utc(double ut11, double ut12, double dut1,
double *utc1, double *utc2)
/*
** - - - - - - - - - -
** i a u U t 1 u t c
** - - - - - - - - - -
**
** Time scale transformation: Universal Time, UT1, to Coordinated
** Universal Time, UTC.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards of Fundamental Astronomy) software collection.
**
** Status: canonical.
**
** Given:
** ut11,ut12 double UT1 as a 2-part Julian Date (Note 1)
** dut1 double Delta UT1: UT1-UTC in seconds (Note 2)
**
** Returned:
** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 3,4)
**
** Returned (function value):
** int status: +1 = dubious year (Note 5)
** 0 = OK
** -1 = unacceptable date
**
** Notes:
**
** 1) ut11+ut12 is Julian Date, apportioned in any convenient way
** between the two arguments, for example where ut11 is the Julian
** Day Number and ut12 is the fraction of a day. The returned utc1
** and utc2 form an analogous pair, except that a special convention
** is used, to deal with the problem of leap seconds - see Note 3.
**
** 2) Delta UT1 can be obtained from tabulations provided by the
** International Earth Rotation and Reference Systems Service. The
** value changes abruptly by 1s at a leap second; however, close to
** a leap second the algorithm used here is tolerant of the "wrong"
** choice of value being made.
**
** 3) JD cannot unambiguously represent UTC during a leap second unless
** special measures are taken. The convention in the present
** function is that the returned quasi JD day UTC1+UTC2 represents
** UTC days whether the length is 86399, 86400 or 86401 SI seconds.
**
** 4) The function iauD2dtf can be used to transform the UTC quasi-JD
** into calendar date and clock time, including UTC leap second
** handling.
**
** 5) 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 iauDat for further details.
**
** Called:
** iauJd2cal JD to Gregorian calendar
** iauDat delta(AT) = TAI-UTC
** iauCal2jd Gregorian calendar to JD
**
** 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)
**
** This revision: 2013 June 18
**
** SOFA release 2017-04-20
**
** Copyright (C) 2017 IAU SOFA Board. See notes at end.
*/
{
int big1;
int i, iy, im, id, js;
double duts, u1, u2, d1, dats1, d2, fd, dats2, ddats, us1, us2, du;
/* UT1-UTC in seconds. */
duts = dut1;
/* Put the two parts of the UT1 into big-first order. */
big1 = ( ut11 >= ut12 );
if ( big1 ) {
u1 = ut11;
u2 = ut12;
} else {
u1 = ut12;
u2 = ut11;
}
/* See if the UT1 can possibly be in a leap-second day. */
d1 = u1;
dats1 = 0;
for ( i = -1; i <= 3; i++ ) {
d2 = u2 + (double) i;
if ( iauJd2cal(d1, d2, &iy, &im, &id, &fd) ) return -1;
js = iauDat(iy, im, id, 0.0, &dats2);
if ( js < 0 ) return -1;
if ( i == - 1 ) dats1 = dats2;
ddats = dats2 - dats1;
if ( fabs(ddats) >= 0.5 ) {
/* Yes, leap second nearby: ensure UT1-UTC is "before" value. */
if ( ddats * duts >= 0 ) duts -= ddats;
/* UT1 for the start of the UTC day that ends in a leap. */
if ( iauCal2jd(iy, im, id, &d1, &d2) ) return -1;
us1 = d1;
us2 = d2 - 1.0 + duts/DAYSEC;
/* Is the UT1 after this point? */
du = u1 - us1;
du += u2 - us2;
if ( du > 0 ) {
/* Yes: fraction of the current UTC day that has elapsed. */
fd = du * DAYSEC / ( DAYSEC + ddats );
/* Ramp UT1-UTC to bring about SOFA's JD(UTC) convention. */
duts += ddats * ( fd <= 1.0 ? fd : 1.0 );
}
/* Done. */
break;
}
dats1 = dats2;
}
/* Subtract the (possibly adjusted) UT1-UTC from UT1 to give UTC. */
u2 -= duts / DAYSEC;
/* Result, safeguarding precision. */
if ( big1 ) {
*utc1 = u1;
*utc2 = u2;
} else {
*utc1 = u2;
*utc2 = u1;
}
/* Status. */
return js;
/*----------------------------------------------------------------------
**
** Copyright (C) 2017
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
** include the prefix "iau" or "sofa" or trivial modifications
** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
** not be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** e) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have
** granted a further right to modify the source code of your
** derived work.
**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or
** by inappropriate modification.
**
** 5. The SOFA software is provided "as is" and SOFA makes no warranty
** as to its use or performance. SOFA does not and cannot warrant
** the performance or results which the user may obtain by using the
** SOFA software. SOFA makes no warranties, express or implied, as
** to non-infringement of third party rights, merchantability, or
** fitness for any particular purpose. In no event will SOFA be
** liable to the user for any consequential, incidental, or special
** damages, including any lost profits or lost savings, even if a
** SOFA representative has been advised of such damages, or for any
** claim by any third party.
**
** 6. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: [email protected]
** By post: IAU SOFA Center
** HM Nautical Almanac Office
** UK Hydrographic Office
** Admiralty Way, Taunton
** Somerset, TA1 2DN
** United Kingdom
**
**--------------------------------------------------------------------*/
}
int iauUtctai(double utc1, double utc2, double *tai1, double *tai2)
/*
** - - - - - - - - - -
** i a u U t c t a i
** - - - - - - - - - -
**
** Time scale transformation: Coordinated Universal Time, UTC, to
** International Atomic Time, TAI.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards of Fundamental Astronomy) software collection.
**
** Status: canonical.
**
** Given:
** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-4)
**
** Returned:
** tai1,tai2 double TAI as a 2-part Julian Date (Note 5)
**
** Returned (function value):
** int status: +1 = dubious year (Note 3)
** 0 = OK
** -1 = unacceptable date
**
** 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
** function 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 and that are too far in the future
** to be trusted. See iauDat for further details.
**
** 4) The function iauDtf2d 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) The returned TAI1,TAI2 are such that their sum is the TAI Julian
** Date.
**
** Called:
** iauJd2cal JD to Gregorian calendar
** iauDat delta(AT) = TAI-UTC
** iauCal2jd Gregorian calendar to JD
**
** 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)
**
** This revision: 2010 September 10
**
** SOFA release 2012-03-01
**
** Copyright (C) 2012 IAU SOFA Board. See notes at end.
**
*/
{
int big1;
int iy, im, id, js, iyt, imt, idt;
double u1, u2, fd, dats, fdt, datst, ddat, z1, z2, a2;
/* Put the two parts of the UTC into big-first order. */
big1 = ( utc1 >= utc2 );
if ( big1 ) {
u1 = utc1;
u2 = utc2;
} else {
u1 = utc2;
u2 = utc1;
}
/* Get TAI-UTC now. */
if ( iauJd2cal(u1, u2, &iy, &im, &id, &fd) ) return -1;
js = iauDat(iy, im, id, fd, &dats);
if ( js < 0 ) return -1;
/* Get TAI-UTC tomorrow. */
if ( iauJd2cal(u1+1.5, u2-fd, &iyt, &imt, &idt, &fdt) ) return -1;
js = iauDat(iyt, imt, idt, fdt, &datst);
if ( js < 0 ) return -1;
/* If today ends in a leap second, scale the fraction into SI days. */
ddat = datst - dats;
if ( fabs(ddat) > 0.5 ) fd += fd * ddat / DAYSEC;
/* Today's calendar date to 2-part JD. */
if ( iauCal2jd(iy, im, id, &z1, &z2) ) return -1;
/* Assemble the TAI result, preserving the UTC split and order. */
a2 = z1 - u1;
a2 += z2;
a2 += fd + dats / DAYSEC;
if ( big1 ) {
*tai1 = u1;
*tai2 = a2;
} else {
*tai1 = a2;
*tai2 = u1;
}
/* Status. */
return js;
/*----------------------------------------------------------------------
**
** Copyright (C) 2012
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
** include the prefix "iau" or "sofa" or trivial modifications
** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
** not be misrepresented; you must not claim that you wrote the
** original software, nor file a patent application for SOFA
** software or algorithms embedded in the SOFA software.
**
** e) These requirements must be reproduced intact in any source
** distribution and shall apply to anyone to whom you have
** granted a further right to modify the source code of your
** derived work.
**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
** disrepute, either by misuse, or use for inappropriate tasks, or
** by inappropriate modification.
**
** 5. The SOFA software is provided "as is" and SOFA makes no warranty
** as to its use or performance. SOFA does not and cannot warrant
** the performance or results which the user may obtain by using the
** SOFA software. SOFA makes no warranties, express or implied, as
** to non-infringement of third party rights, merchantability, or
** fitness for any particular purpose. In no event will SOFA be
** liable to the user for any consequential, incidental, or special
** damages, including any lost profits or lost savings, even if a
** SOFA representative has been advised of such damages, or for any
** claim by any third party.
**
** 6. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: [email protected]
** By post: IAU SOFA Center
** HM Nautical Almanac Office
** UK Hydrographic Office
** Admiralty Way, Taunton
** Somerset, TA1 2DN
** United Kingdom
**
**--------------------------------------------------------------------*/
}
int iauDat(int iy, int im, int id, double fd, double *deltat )
/*
** - - - - - - -
** i a u D a t
** - - - - - - -
**
** For a given UTC date, calculate delta(AT) = TAI-UTC.
**
** :------------------------------------------:
** : :
** : IMPORTANT :
** : :
** : A new version of this function must be :
** : produced whenever a new leap second is :
** : announced. There are four items to :
** : change on each such occasion: :
** : :
** : 1) A new line must be added to the set :
** : of statements that initialize the :
** : array "changes". :
** : :
** : 2) The parameter IYV must be set to :
** : the current year. :
** : :
** : 3) The "Latest leap second" comment :
** : below must be set to the new leap :
** : second date. :
** : :
** : 4) The "This revision" comment, later, :
** : must be set to the current date. :
** : :
** : Change (2) must also be carried out :
** : whenever the function is re-issued, :
** : even if no leap seconds have been :
** : added. :
** : :
** : Latest leap second: 2012 June 30 :
** : :
** :__________________________________________:
**
** This function is part of the International Astronomical Union's
** SOFA (Standards Of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** iy int UTC: year (Notes 1 and 2)
** im int month (Note 2)
** id int day (Notes 2 and 3)
** fd double fraction of day (Note 4)
**
** Returned:
** deltat double TAI minus UTC, seconds
**
** Returned (function value):
** int status (Note 5):
** 1 = dubious year (Note 1)
** 0 = OK
** -1 = bad year
** -2 = bad month
** -3 = bad day (Note 3)
** -4 = bad fraction (Note 4)
**
** Notes:
**
** 1) UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper
** to call the function with an earlier date. If this is attempted,
** zero is returned together with a warning status.
**
** Because leap seconds cannot, in principle, be predicted in
** advance, a reliable check for dates beyond the valid range is
** impossible. To guard against gross errors, a year five or more
** after the release year of the present function (see parameter
** IYV) is considered dubious. In this case a warning status is
** returned but the result is computed in the normal way.
**
** For both too-early and too-late years, the warning status is
** j=+1. This is distinct from the error status j=-1, which
** signifies a year so early that JD could not be computed.
**
** 2) If the specified date is for a day which ends with a leap second,
** the UTC-TAI value returned is for the period leading up to the
** leap second. If the date is for a day which begins as a leap
** second ends, the UTC-TAI returned is for the period following the
** leap second.
**
** 3) The day number must be in the normal calendar range, for example
** 1 through 30 for April. The "almanac" convention of allowing
** such dates as January 0 and December 32 is not supported in this
** function, in order to avoid confusion near leap seconds.
**
** 4) The fraction of day is used only for dates before the
** introduction of leap seconds, the first of which occurred at the
** end of 1971. It is tested for validity (0 to 1 is the valid
** range) even if not used; if invalid, zero is used and status
** j=-4 is returned. For many applications, setting fd to zero is
** acceptable; the resulting error is always less than 3 ms (and
** occurs only pre-1972).
**
** 5) The status value returned in the case where there are multiple
** errors refers to the first error detected. For example, if the
** month and day are 13 and 32 respectively, j=-2 (bad month)
** will be returned.
**
** 6) In cases where a valid result is not available, zero is returned.
**
** References:
**
** 1) For dates from 1961 January 1 onwards, the expressions from the
** file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used.
**
** 2) The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of
** the 1992 Explanatory Supplement.
**
** Called:
** iauCal2jd Gregorian calendar to Julian Day number
**
** This revision: 2012 June 14
**
** SOFA release 2012-03-01
**
** Copyright (C) 2012 IAU SOFA Board. See notes at end.
*/
{
/* Release year for this version of iauDat */
#define IYV (2012)
/* Reference dates (MJD) and drift rates (s/day), pre leap seconds */
static const double drift[][2] = {
{ 37300.0, 0.0012960 },
{ 37300.0, 0.0012960 },
{ 37300.0, 0.0012960 },
{ 37665.0, 0.0011232 },
{ 37665.0, 0.0011232 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 38761.0, 0.0012960 },
{ 39126.0, 0.0025920 },
{ 39126.0, 0.0025920 }
};
/* Number of Delta(AT) expressions before leap seconds were introduced */
#define NERA1 ((int) (sizeof drift / sizeof (double) / 2))
/* Dates and Delta(AT)s */
static const struct {
int iyear, month;
double delat;
} changes[] = {
{ 1960, 1, 1.4178180 },
{ 1961, 1, 1.4228180 },
{ 1961, 8, 1.3728180 },
{ 1962, 1, 1.8458580 },
{ 1963, 11, 1.9458580 },
{ 1964, 1, 3.2401300 },
{ 1964, 4, 3.3401300 },
{ 1964, 9, 3.4401300 },
{ 1965, 1, 3.5401300 },
{ 1965, 3, 3.6401300 },
{ 1965, 7, 3.7401300 },
{ 1965, 9, 3.8401300 },
{ 1966, 1, 4.3131700 },
{ 1968, 2, 4.2131700 },
{ 1972, 1, 10.0 },
{ 1972, 7, 11.0 },
{ 1973, 1, 12.0 },
{ 1974, 1, 13.0 },
{ 1975, 1, 14.0 },
{ 1976, 1, 15.0 },
{ 1977, 1, 16.0 },
{ 1978, 1, 17.0 },
{ 1979, 1, 18.0 },
{ 1980, 1, 19.0 },
{ 1981, 7, 20.0 },
{ 1982, 7, 21.0 },
{ 1983, 7, 22.0 },
{ 1985, 7, 23.0 },
{ 1988, 1, 24.0 },
{ 1990, 1, 25.0 },
{ 1991, 1, 26.0 },
{ 1992, 7, 27.0 },
{ 1993, 7, 28.0 },
{ 1994, 7, 29.0 },
{ 1996, 1, 30.0 },
{ 1997, 7, 31.0 },
{ 1999, 1, 32.0 },
{ 2006, 1, 33.0 },
{ 2009, 1, 34.0 },
{ 2012, 7, 35.0 }
};
/* Number of Delta(AT) changes */
const int NDAT = sizeof changes / sizeof changes[0];
/* Miscellaneous local variables */
int j, i, m;
double da, djm0, djm;
/* Initialize the result to zero. */
*deltat = da = 0.0;
/* If invalid fraction of a day, set error status and give up. */
if (fd < 0.0 || fd > 1.0) return -4;
/* Convert the date into an MJD. */
j = iauCal2jd(iy, im, id, &djm0, &djm);
/* If invalid year, month, or day, give up. */
if (j < 0) return j;
/* If pre-UTC year, set warning status and give up. */
if (iy < changes[0].iyear) return 1;
/* If suspiciously late year, set warning status but proceed. */
if (iy > IYV + 5) j = 1;
/* Combine year and month to form a date-ordered integer... */
m = 12*iy + im;
/* ...and use it to find the preceding table entry. */
for (i = NDAT-1; i >=0; i--) {
if (m >= (12 * changes[i].iyear + changes[i].month)) break;
}
/* Get the Delta(AT). */
da = changes[i].delat;
/* If pre-1972, adjust for drift. */
if (i < NERA1) da += (djm + fd - drift[i][0]) * drift[i][1];
/* Return the Delta(AT) value. */
*deltat = da;
/* Return the status. */
return j;
/*----------------------------------------------------------------------
**
** Copyright (C) 2012
** Standards Of Fundamental Astronomy Board
** of the International Astronomical Union.
**
** =====================
** SOFA Software License
** =====================
**
** NOTICE TO USER:
**
** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
** CONDITIONS WHICH APPLY TO ITS USE.
**
** 1. The Software is owned by the IAU SOFA Board ("SOFA").
**
** 2. Permission is granted to anyone to use the SOFA software for any
** purpose, including commercial applications, free of charge and
** without payment of royalties, subject to the conditions and
** restrictions listed below.
**
** 3. You (the user) may copy and distribute SOFA source code to others,
** and use and adapt its code and algorithms in your own software,
** on a world-wide, royalty-free basis. That portion of your
** distribution that does not consist of intact and unchanged copies
** of SOFA source code files is a "derived work" that must comply
** with the following requirements:
**
** a) Your work shall be marked or carry a statement that it
** (i) uses routines and computations derived by you from
** software provided by SOFA under license to you; and
** (ii) does not itself constitute software provided by and/or
** endorsed by SOFA.
**
** b) The source code of your derived work must contain descriptions
** of how the derived work is based upon, contains and/or differs
** from the original SOFA software.
**
** c) The names of all routines in your derived work shall not
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** thereof such as changes of case.
**
** d) The origin of the SOFA components of your derived work must
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**
** e) These requirements must be reproduced intact in any source
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** derived work.
**
** Note that, as originally distributed, the SOFA software is
** intended to be a definitive implementation of the IAU standards,
** and consequently third-party modifications are discouraged. All
** variations, no matter how minor, must be explicitly marked as
** such, as explained above.
**
** 4. You shall not cause the SOFA software to be brought into
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**
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** claim by any third party.
**
** 6. The provision of any version of the SOFA software under the terms
** and conditions specified herein does not imply that future
** versions will also be made available under the same terms and
** conditions.
*
** In any published work or commercial product which uses the SOFA
** software directly, acknowledgement (see www.iausofa.org) is
** appreciated.
**
** Correspondence concerning SOFA software should be addressed as
** follows:
**
** By email: [email protected]
** By post: IAU SOFA Center
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**
**--------------------------------------------------------------------*/
}
