JOUR A PARTIR D'UNE DATE MM/JJ/YYYY

#include<stdio.h>

bool isleap(int n){
    if(n<1732)
      return (!(n%4));
    return (!(n%4)&&(n%100))||!(n%400);
    }
int mounths[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
char *days[7]={"Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"};
char* M[]={"","January","February","March","April","May","June","July","August","September","October","November","December"};


bool isvalide(int m,int d,int y){
   if(d > 2 && d < 14 && m == 9 && y == 1752)
     return false;
   return ( d <= mounths[m]+isleap(y)*(m == 2) && m < 13 );
   }
int main(){
   int d,m,y;
   printf("Enter the date that you want to know the correspondant day of week in this
form : mm dd yyyy\n mm:mounth \n dd : day\n yyyy:year\n");//ligne ajoutée en réponse a la demande de "ndubien" 

  
   scanf("%d%d%d",&m,&d,&y);
   while(m != 0 && d != 0 && y != 0){
       if(!isvalide(m,d,y))
         printf("%d/%d/%d is an invalid date.\n",m,d,y);
       else{
          long L=0;
          for(int i=1;i<y;i++)
             L+=365+isleap(i);
          for(int i=1;i<m;i++)
             if(i == 2)
               L+=28+isleap(y);
             else
               L+=mounths[i];
          L+=d+4;
          L-=11*((y>1752) || (y==1752 && m>9) ||(y==1752 && m==9 && d>2));

          L%=7;
          printf("%s %d, %d is a %s\n",M[m],d,y,days[L]);

      }
       scanf("%d%d%d",&m,&d,&y);
   }


   return 0;

}