epochbk.c

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/*****************************************************************
 *
 *  NSSDC/CDF                           EPOCHbreakdown.
 *
 *  Version 2.0, 10-Jul-91, ST Systems (STX)
 *
 *  Modification history:
 *
 *   V1.0 ~11-Feb-91, J Love    Original version (for CDF V2.0).  Used
 *              algorithm from EPOCH_BREAKDOWN.F (author
 *              unknown).
 *   V1.1   9-Jul-91, J Love    Added include of 'math.h'.
 *   V2.0  10-Jul-91, J Love    Renamed (was EPOCH_BREAKDOWN.C in CDF V2.0
 *              distribution).
 *
 *******************************************************************/
 
#include <math.h>
 
void EPOCHbreakdown(epoch, year, month, day, hour, minute, second, msec)
double epoch;
long *year, *month, *day, *hour, *minute, *second, *msec;
{
    long jd, i, j, k, l, n;
    double msecAD, secondAD, minuteAD, hourAD, dayAD;
 
    msecAD = epoch;
    secondAD = msecAD / 1000.0;
    minuteAD = secondAD / 60.0;
    hourAD = minuteAD / 60.0;
    dayAD = hourAD / 24.0;
 
    jd = 1721060 + dayAD;
    l = jd + 68569;
    n = 4 * l / 146097;
    l = l - (146097 * n + 3) / 4;
    i = 4000 * (l + 1) / 1461001;
    l = l - 1461 * i / 4 + 31;
    j = 80 * l / 2447;
    k = l - 2447 * j / 80;
    l = j / 11;
    j = j + 2 - 12 * l;
    i = 100 * (n - 49) + i + l;
 
    *year = i;
    *month = j;
    *day = k;
 
    *hour = fmod(hourAD, 24.0);
    *minute = fmod(minuteAD, 60.0);
    *second = fmod(secondAD, 60.0);
    *msec = fmod(msecAD, 1000.0);
 
    return;
}