计算2000年以后的日期对应的星期子程序

 

unsigned char today_week(unsigned char year,unsigned char month, unsigned char date)
{
 unsigned int doy = 0;
 unsigned char i,j;
 unsigned char temp = 12;
  
 for(j=0;j {
  if(is_leap(j))
   doy += 365;
  else
   doy += 366;
 }

 for(i=1;i  {
   if(i==1)
    doy += 31;
   else if(i==2)
   {
    if(is_leap(year))
     doy += 28;
    else
     doy += 29;
   }
   else if(i==3)
    doy += 31;
   else if(i==4)
    doy += 30;
   else if(i==5)
    doy += 31;
   else if(i==6)
    doy += 30;
   else if(i==7)
    doy += 31;
   else if(i==8)
    doy += 31;
   else if(i==9)
    doy += 30;
   else if(i==10)
    doy += 31;
   else if(i==11)
    doy += 30;
   else if(i==12)
    doy += 31;
  }
  doy += date;

 return (doy+5) % 7;
}

unsigned char is_leap(unsigned char year)      //check for leap year
{
 unsigned int temp = 2000;
 temp = temp + year;
    if (!(temp%100))
        return (char)(temp%400);
    else
        return (char)(temp%4);
}

 

其实程序本身隐含着一个参考日期对应的星期，那就是2000年1月1日，对应周六，计算这以后的日期对应的星期其实就是累加的方法计算的.