Мне нужна полная программа на C++ для вычисления разницы между двумя датами в году месяце и дне ?

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я студент-информатик, и я написал программу, и я не знаю ошибки ? помоги мне!!

Что я уже пробовал:

private int[] monthDay = new int[12] { 31, -1, 31, 30, 31, 30, 31, 31, 30, 31, 30,
31 };
private DateTime fromDate;
private DateTime toDate;
private int year;
private int month;
private int day;

public DateDifference(DateTime d1, DateTime d2)

	if (d1 >d2)
{
    this.fromDate = d2;
    this.toDate = d1;
}
else
{
    this.fromDate = d1;
    this.toDate = d2;
}

	increment = 0; 
if (this.fromDate.Day > this.toDate.Day)
{ 
    increment = this.monthDay[this.fromDate.Month - 1]; 
}

if (increment== -1)
{
    if (DateTime.IsLeapYear(this.fromDate.Year))
    {
        increment = 29;
    } 
    else
    {
        increment = 28;
    }
}

if (increment != 0)
{    
    day = (this.toDate.Day+ increment) - this.fromDate.Day;
    increment = 1; 
}
else
{       
    day = this.toDate.Day - this.fromDate.Day;
}

if ((this.fromDate.Month + increment) > this.toDate.Month)
{   
    this.month = (this.toDate.Month+ 12) - (this.fromDate.Month + increment);
       increment = 1;
}
else
{    
    this.month = (this.toDate.Month) - (this.fromDate.Month + increment);
    increment = 0;
}

this.year = this.toDate.Year - (this.fromDate.Year + increment);


public int year;
public int month;
public int day;

public override string ToString()
{    
    return this.year + "Year(s), " + this.month + " month(s), " + this.day + " day(s)";
}

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