Установить дату SetDate() Метод должен содержать три параметра: день, месяц, год

#include <iostream>
#include <iomanip>
using namespace std;
struct Date {
  int day, month, year;
  int lastNumber();
  int chekDate(); 
  int isLeap();
  int CountDay();
  int DayWeek();
  int Friday13();
  int SetDate();
  int ShowDate();
};
int Date::CountDay(){
    int daysPassed;
    year--;
    daysPassed = year * 365 + year / 4 - year / 100 + year / 400;
    year++;
    for (int i = 1; i < month; i++)
        daysPassed += 28 + (i + i / 8) % 2 + 2 % i + 1 / i * 2;
    if (month > 2 && year % 4 == 0 && (year % 100 != 0 || year % 400 == 0))
        daysPassed++;
    daysPassed += day - 1;
    return daysPassed;
}
int Date::isLeap(){
  if (year % 4 == 0 || year % 400 == 0 || year % 100 == 0){
    return true;
  }
  else {
    return false;
  }
}
int Date::lastNumber() {
    switch (month) {
      case 1:
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
        return 31;
        break;
      case 4:
      case 6:
      case 9:
      case 11:
        return 30;
        break;
      case 2:
        if (isLeap() == true) {
          return 28;
        }
        else {
          return 29;
        }
    }
  return 0;
}
int Date::chekDate() {
    if (year > 0 && month > 0 && month <= 12 && day <= lastNumber() && day > 0) {
      return true;
    }
    else {
      return false;
    }
  return 0;
}
int Date::DayWeek(){   
    int dayOfWeek = (CountDay()+1) % 7;
    return (dayOfWeek);
}
int Date::Friday13() {   
  Date d = {13, month, year};
  if (day > 13)
    d.month++;
    while(d.DayWeek() != 5) {
      d.month++;
      if (d.month > 12) {
        d.month = 1;
        d.year++;
        }
    }
    return d.CountDay() - CountDay();
}
 
int Date::SetDate() {
  Date d,m,y;
  if (chekDate() == false) {
    return false;
  }
  else {
    SetDate(day , month , year) ;
    return true;
  }
}
 
 
 
int Date::ShowDate() {
  if (SetDate() == false) {
    cout << endl << day << " " << month<< " " << year;
  }
  else {
    cout << endl << setw(2) << setfill('0') << day << "." << setw(2) << setfill('0') << month << setw(4) << setfill('0') << "." << year;
  }
}
int main() {
  Date time;
  cout << "Entered date";
  cin >> time.day >> time.month >> time.year;
  cout << endl << endl << endl;
  if (time.chekDate() == false){
    time.day = 1; time.month = 1; time.year = 1;
    cout << setw(2) << setfill('0') <<  time.day << "." << setw(2) << setfill('0') << time.month << "." << time.year;
  }
  cout << endl << "time.CountDay: " << time.CountDay() << "\n";
  cout << "time.DayWeek() " << time.DayWeek();
  cout << endl << "13 : " << time.Friday13();
  cout << endl << time.ShowDate();
  return 0;
}

bool is_leap_year(int year)
{
  if (year % 4 != 0)   return false;
  if (year % 100 != 0) return true;
  if (year % 400 == 0) return true;
  return false;
}
 
int days_in_month(int y, int m)
{
  switch (m)
  {
    case 4: case 6: case 9: case 11: return 30;
    case 2:  return is_leap_year(y) ? 29 : 28;
    default: return 31;
  }
}
 
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 
bool is_correct_date(int y, int m, int d)
{
  return (m > 0 && m < 13 && d <= days_in_month(y, m));
}