int eraDat	(	int	iy,
		int	im,
		int	id,
		double	fd,
		double *	deltat
	)

Definition at line 3 of file dat.c.

References eraCal2jd(), and i.

Referenced by eraD2dtf(), eraDtf2d(), eraUt1utc(), eraUtctai(), eraUtcut1(), palDat(), and t_dat().

{
/* Release year for this version of eraDat */
   enum { IYV = 2015};

/* 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 */
   enum { 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       },
      { 2015,  7, 36.0       }
   };

/* Number of Delta(AT) changes */
   enum { NDAT = (int) (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 = eraCal2jd(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;
   }

/* Prevent underflow warnings. */
   if (i < 0) return -5;

/* 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;

}

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