Grazie!! Ho risolto, non me ne ero proprio accorto
#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <iomanip>

using namespace std;

int main()
{
srand(time(NULL));
int x=rand()%6+1;
switch (x) {
case 1:
cout<<x<<") Lunedi";
break;
case 2:
cout<<x<<") Martedi";
break;
case 3:
cout<<x<<") Mercoledi";
break;
case 4:
cout<<x<<") Giovedi";
break;
case 5:
cout<<x<<") Venerdi";
break;
case 6:
cout<<x<<") Sabato";
break;
case 7:
cout<<x<<") Domenica";
break;
}
return 0;
}