Hier soir, j'ai essayé sous DOS sur mon vieux DX4/100.
L'exemple Borland m'a donné Monday pour le Year 2002, month 4, day 15.
 
C'est bien  
#include <stdio.h>
#include <time.h>
 
 char *wday[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
  "Thursday", "Friday", "Saturday", "Unknown"};
 
int main(void)
{
    struct tm time_check;
    int year, month, day;
 
/*  Input a year, month and day to find the weekday for */
    printf("Year:  " );
    scanf("%d", &year);
    printf("Month: " );
    scanf("%d", &month);
    printf("Day:   " );
    scanf("%d", &day);
 
/*  load the time_check structure with the data */
 
    time_check.tm_year = year - 1900;
    time_check.tm_mon  = month - 1;
    time_check.tm_mday = day;
    time_check.tm_hour = 0;
    time_check.tm_min  = 0;
    time_check.tm_sec  = 1;
    time_check.tm_isdst = -1;
 
/*  call mktime to fill in the weekday field of the structure */
    if (mktime(&time_check) == -1)
       time_check.tm_wday = 7;
 
/*  print out the day of the week */
    printf("That day is a %s\n", wday[time_check.tm_wday]);
    return 0;
}