#include <iostream>
#include <string>
#include <fstream>
#include <cassert>
#include "boost/date_time/gregorian/gregorian.hpp"
using namespace std;
using namespace boost::gregorian;

int main() {
   date d(from_undelimited_string(string{"20180101"}));
   string ext = to_iso_extended_string(d);
   assert(ext == "2018-01-01");
   for (day_iterator d{start_date}; d <= end_date; ++d) {
        ofstream ofs(argv[3] + to_iso_extended_string(*d), std::ofstream::out);
   }
}