Переделать программу в ООП

#include <iostream>
#include <fstream>
using namespace std;
 
typedef struct Date
{
    int day, month, year;
    bool valid;
} Date;
 
bool checkDate(Date* d)
{
    d->valid = true;
    if(d->day > 30 || d->month > 12 || d->day < 1 || d->month < 1 || d->year < 1)
        d->valid = false;
    return d->valid;
}
 
void printDate(FILE* f, Date d)
{
    ofstream fout;
    fout <<d.day <<d.month <<d.year <<endl;
}
 
Date readDate(FILE* f)
{
    Date d;
    cout <<"Enter date in format DD.MM.YYYY: " <<endl;
    
    if(fscanf(f, "%d.%d.%d", &d.day, &d.month, &d.year) != 3)
    {
        d.day = d.month = d.year = 0;
        d.valid = false;
    }
    checkDate(&d);
    return d;
}
 
long getDays(Date d)
{
    return d.year*365 + d.month*30 + d.day;
}
 
long subtractDates(Date d1, Date d2)
{
    return getDays(d1) - getDays(d2);
}
 
 
int main(int argc, char** argv)
{
    Date d1 = readDate(stdin);
    Date d2 = readDate(stdin);
 
    if(!d2.valid)
    {
        cout <<"You have entered an invalid date!" <<endl;
        Date d2 = readDate(stdin);
    } else
    {
        cout <<"Second date: " <<endl;
        printDate(stdout, d2);
        cout <<"Days: " <<getDays(d2) <<endl;
    }
 
    if(!d1.valid)
    {
        cout <<"You have entered an invalid date!" <<endl;
    } else
    {
        cout <<"First date: " <<endl;
        printDate(stdout, d1);
        cout <<"Days: " <<getDays(d1) <<endl;
    }
 
    if(!d2.valid)
    {
        cout <<"You have entered an invalid date!" <<endl;
    } else
    {
        cout <<"Second date: " <<endl;
        printDate(stdout, d2);
        cout <<"Days: " <<getDays(d2) <<endl;
    }
 
    if((d1.valid && d2.valid))
    {
        cout <<"The difference between dates (days): " <<abs(subtractDates(d1, d2)) <<endl;
    }
 
    return 0;
}