eccodes/src/grib_date.c

/*
 * Copyright 2005-2018 ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

/***************************************************************************
 *   Enrico Fucile                                                            *
 *                                                                         *
 ***************************************************************************/
#include "grib_api_internal.h"

#define ROUND(a)     ((a) >=0 ? (long)((a)+0.5) : (long) ((a)-0.5))
int grib_julian_to_datetime(double jd,long *year,long* month,long* day,
        long *hour,long *minute,long *second)
{
    long z,a,alpha,b,c,d,e;
    double dday;
    double f;
    long s;

    jd+=0.5;
    z=(long)jd;
    f=jd-z;

    if (z < 2299161) a=z;
    else {
        alpha=(long)((z-1867216.25)/36524.25);
        a=z+1+alpha-(long)(((double)alpha)/4);
    }
    b=a+1524;
    c=(long)((b-122.1)/365.25);
    d=(long)(365.25*c);
    e=(long)(((double)(b-d))/30.6001);

    dday=b-d-(long)(30.6001*e)+f;
    *day=(long)dday;
    dday-=*day;

#if 1
    /* ANF-CG 02.03.2012 */
    s=ROUND((double)(dday*86400)); /* total in sec , no msec*/
    *hour=(long)s/3600;
    *minute=(long)((s % 3600)/60);
    *second = (long)(s % 60);
#else
    /* Old algorithm, now replaced by above. See GRIB-180 */
    dhour=dday*24;
    *hour=(long)dhour;
    dhour-=*hour;
    dminute=dhour*60;
    *minute=(long)dminute;
    *second=(long)((dminute-*minute)*60);
#endif

    if (e<14) *month=e-1;
    else *month=e-13;

    if (*month>2) *year=c-4716;
    else *year=c-4715;

    return GRIB_SUCCESS;
}

int grib_datetime_to_julian(long year,long month,long day,
        long hour,long minute,long second,double* jd)
{
    return grib_datetime_to_julian_d(year,month,day,hour,minute,second,jd);
}

/* This version can deal with seconds provided as a double. Supporting milliseconds etc */
int grib_datetime_to_julian_d(
        long year,long month,long day,long hour,long minute,
        double second, double* jd)
{
    double a,b,dday;
    long y,m;

    dday=(double)(hour*3600+minute*60+second)/86400.0+day;

    if ( month < 3) {
        y=year-1;
        m=month+12;
    } else {
        y=year;
        m=month;
    }
    a=(long)(((double)y)/100);

    if ( y > 1582 ) b=2-a+(long)(a/4);
    else if (y == 1582) {
        if (m > 10) b=2-a+(long)(a/4);
        else if (m == 10) {
            if (day >14) b=2-a+(long)(a/4);
            else b=0;
        }
        else b=0;
    }
    else b=0;

    *jd=(long)(365.25*(y+4716))+ (long)(30.6001*(m+1))+dday+b-1524.5;

    return GRIB_SUCCESS;
}

long grib_julian_to_date(long jdate)
{
    long x,y,d,m,e;
    long day,month,year;

    x = 4 * jdate - 6884477;
    y = (x / 146097) * 100;
    e = x % 146097;
    d = e / 4;

    x = 4 * d + 3;
    y = (x / 1461) + y;
    e = x % 1461;
    d = e / 4 + 1;

    x = 5 * d - 3;
    m = x / 153 + 1;
    e = x % 153;
    d = e / 5 + 1;

    if( m < 11 )
        month = m + 2;
    else
        month = m - 10;

    day = d;
    year = y + m / 11;

    return year * 10000 + month * 100 + day;
}

long grib_date_to_julian(long ddate)
{
    long  m1,y1,a,b,c,d,j1;

    long month,day,year;

    /*Asserts(ddate > 0);*/

    year = ddate / 10000;
    ddate %= 10000;
    month  = ddate / 100;
    ddate %= 100;
    day = ddate;

    /*  if (year < 100) year = year + 1900; */

    if (month > 2)
    {
        m1 = month - 3;
        y1 = year;
    }
    else
    {
        m1 = month + 9;
        y1 = year - 1;
    }
    a = 146097*(y1/100)/4;
    d = y1 % 100;
    b = 1461*d/4;
    c = (153*m1+2)/5+day+1721119;
    j1 = a+b+c;

    return(j1);
}

/*
   void basedate_to_verifydate(gribsec1 *s1,request *r)
   {
   int bdate,vdate,cdate,vd,vtime,vstep;

   bdate = (s1->century-1)*1000000 + s1->year * 10000 + s1->month * 100 + s1->day;
   cdate = date_to_julian (bdate);
   vtime = cdate * 24 + s1->p1*units[s1->time_unit];
   vd    = vtime / 24;
   vdate = julian_to_date (vd,mars.y2k);
   vtime = vtime % 24;
   vstep = 0;

   set_value(r,"DATE","%d",vdate);
   set_value(r,"TIME","%02d00",vtime);
   set_value(r,"STEP","%d",vstep);
   }
 */