Funktion - MyGetWeekday

Kurzbeschreibung

Diese Funktion berechnet zu einem gegebenen Datum den Wochentag mit Hilfe der Gaußschen Wochentagsformel.

• stc_date date: Datum, zu dem der Wochentag berechnet werden soll.

• Nummer des Wochentages: 0 = Samstag, 1 = Sonntag, ... 6 = Freitag

Code

#include <math.h>
 
typedef struct{
  uint16_t year;
  uint8_t  month;
  uint8_t  day;
} stc_date;
 
uint8_t MyGetWeekday(stc_date date)
{
  // Calculate weekday of a given date by using gauss algorithm
  uint8_t  h    = 0;            // Weekday
  uint16_t year = (date).year;  // Year (4 digits)
  uint8_t  m    = (date).month; // Month
  uint8_t  q    = (date).day;   // Day
  if (m < 3)  // January = 13th, February = 14th of previous year 
  {
    m += 12;
    year--;
  }
 
  uint8_t J = (uint8_t) ((uint16_t) year / (uint16_t) 100);                   // Century (first 2 digits)
  uint8_t K = (uint8_t) ((uint16_t) year - ((uint16_t) J * (uint16_t) 100));  // year in century (last 2 digits)
 
  h = ((q + floor(((m+1)*26)/10) + K + floor(K/4) + (J/4) - (2*J))); // applying Gauss formula
  h %= 7;
  return h;
}