isWeekend

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int isWeekend(const char*date)
{
   int day_num[2][13] = { { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
                          { 1, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } };
   int i;

   int tmp1 = 0;
   int tmp2 = 0;
   int year_diff = 0;

   int total_day = 0;
   char szYY[5];
   char szMM[3];
   char szDD[3];
   int iYY;
   int iMM;
   int iDD;
   strncpy(szYY, date, 4);
   iYY = atoi(szYY);
   strncpy(szMM, date + 4, 2);
   iMM = atoi(szMM);
   strncpy(szDD, date + 6, 2);
   iDD = atoi(szDD);

   year_diff = iYY - 2009;
   if(year_diff == 0){
      for(i = 1; i < iMM; i++){
         tmp2 += day_num[0][i];
      }
      tmp2 += iDD;

      tmp1 = 4;
      total_day = tmp2 -tmp1;
      if( total_day%7 != 0) /* Not Weekend */
         return 0;
      else /* Weekend */
         return 1;

   }else if(year_diff == 1){
      for(i = 2; i <= 12; i++){
         tmp1 += day_num[0][i];
      }
      tmp1 += (31-4);

      for(i = 1; i < iMM; i++){
         tmp2 += day_num[0][i];
      }
      tmp2 += iDD;

      total_day = tmp2 + tmp1;
      if( total_day%7 != 0) /* Not Weekend */
         return 0;
      else /* Weekend*/
         return 1;

   }else if(year_diff >= 2){
      for(i = 2; i <= 12; i++){
         tmp1 += day_num[0][i];
      }
      tmp1 += (31-4);

      for(i = 1; i < iMM; i++){
         tmp2 += day_num[0][i];
      }
      tmp2 += iDD;

      total_day = tmp2 + tmp1;

      for( i = 2010; i < iYY; i++){
         if(((i%4 == 0) && (i%100 != 0)) || (i%400 == 0))
            total_day += 366;
         else
            total_day += 365;
      }

      if(total_day%7 != 0) /* Not Weekend */
         return 0;
      else
         return 1; /* Weekend */
   }
   return -1;
}



int main(int argc, char *argv[])
{
   if(isWeekend(argv[1]))
      printf("%s is weekend\n", argv[1]);
   else
      printf("%s is not weekend\n", argv[1]);

   return 0;
}