C++实现 “时间日期”类的小项目，及运算符重载

class Date
{
public:
	int GetMonthDay(int year,int month)
	{
		int MonthDays[13] = { 0,31,28,31,30,31,30,31,31,30,31,30,31 };
		if (month == 2 && (year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
		{
			return 29;
		}
		return MonthDays[month];
	}
	Date(int year = 0, int month = 1,int day = 1)
	{
		if (year >= 0 
			&& month >= 1 && month <= 12 
			&& day >= 1 && day <=GetMonthDay(year,month))
		{
			_year = year;
			_month = month;
			_day = day;
		}
		else 
		{
			cout << "非法日期" << endl;
		}
	}
	
	Date(const Date& d)
	{
		_year = d._year;
		_month = d._month;
		_day = d._day;
	}

	bool operator<(const Date& d)
	{
		if (_year < d._year)
			return true;
		else if (_year == d._year && _month < d._month)
			return true;
		else if (_year == d._year && _month == d._month && _day < d._day)
			return true;

		return false;
	}

	bool operator==(const Date& d)
	{
		return _year == d._year && _month == d._month && _day == d._day;
	}
	  
	bool operator<=(const Date& d)//bool operator<=(Date* this, const Date& d)
	{
		/*if (_year < d._year)
			return true;
		else if (_year == d._year && _month < d._month)
			return true;
		else if (_year == d._year && _month == d._month && _day <= d._day)
			return true;

		return false;*/
		//或者   *this就是d1，d就是d2
		return *this < d || *this == d;
	}

	bool operator>(const Date& d)
	{
		return !(*this <= d);
	}
	
	bool operator>=(const Date& d)
	{
		return !(*this < d);
	}
	
	bool operator!=(const Date& d)
	{
		return !(*this == d);
	}

	Date& operator=(const Date& d)
	{
		if (this != &d)
		{
			_year = d._year;
			_month = d._month;
			_day = d._day;
		}
		return *this;

	}
	Date operator+(int day)
	{
		Date ret(*this);//d1拷贝构造 ret
		ret._day += day;
		while (ret._day > GetMonthDay(ret._year, ret._month))
		{
			ret._day -= GetMonthDay(ret._year, ret._month);
			ret._month++;

			if (ret._month == 13)
			{
				ret._year++;
				ret._month = 1;
			}
		}
		return ret;
	}

	Date& operator-=(int day)
	{
		
		_day -= day;
		while (_day <= 0)
		{
			
			_month--;
			if (_month == 0)
			{
				_year--;
				_month = 12;
			}
			_day += GetMonthDay(_year, _month);
		}
		return *this;
	}

	Date operator-(int day)
	{
		Date ret = *this;
		ret._day -= day;
		ret._month--;
		while(ret._day <= 0)
		{
			ret._month--;
			if (ret._month == 0)
			{
				ret._year--;
				ret._month = 12;
			}
			ret._day += GetMonthDay(ret._year, ret._month);
		}
		return ret;
	}

	void Print()
	{
		cout << _year << "-" << _month << "-" << _day<<endl;
	}
		
private:
	int _year;
	int _month;
	int _day;

};

int main()
{
	Date d1(2022, 2, 3);
	d1.Print();

	Date d2(2020, 2, 29);
	d2.Print();

	
	cout << (d1 < d2) << endl;
	cout << (d1 > d2) << endl;
	cout << (d1 == d2) << endl;
	cout << (d1 != d2) << endl;
	cout << (d1 <= d2) << endl;
	cout << (d1 >= d2) << endl;

	Date d3(2021, 1, 1);
	d3.Print();

	Date d4 = d3 + 400;
	d4.Print();

	Date d5 = d4 -= 400;
	d5.Print();
	//Date d1(2023, 11, 22);
	//d1.Print();

	//Date d2(d1);
	//d2.Print();

	//Date d3;
	//d3 = d1;
	//d3.Print();


	return 0;
}