日期类（仅提供类的实现，主函数没写）

#include<iostream>
using namespace std;
int Year[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
class Date
{
public:
	Date(int year1 = 1900, int month1 = 1, int day1 = 1) // 全缺省的构造函数
	{
		if (year1 >= 0 && month >= 1 && month1 <= 12 && day1 >= 1 && day1 <= GetMonthDay(year1, month1))
		{
			year = year1;
			month = month1;
			day = day1;
		}
		else
		{
			cout << "非法日期" << endl;
			cout << year << "年" << month << "月" << day << "日" << endl;
		}
	}
	inline int GetMonthDay(int year1, int month1) // 获取某年某月的天数
	{
		if ((year1 % 4 == 0 && year1 % 100 != 0) || year1 % 400 == 0)
		{
			if (month1 == 2)
				return 29;
			else
				return Year[month1];
		}
		else
			return Year[month1];
	}
	Date(const Date& d) //拷贝构造函数
	{
		year = d.year;
		month = d.month;
		day = d.day;
	}
	Date& operator=(const Date& d)
	{
		year = d.year;
		month = d.month;
		day = d.day;
	}
	~Date();
	Date& operator+=(int day1)
	{
		if (day1 < 0)
		{
			//复用operator-=
			*this -= -day1;
		}
		else
		{
			day += day1;

			/*
			天数加上去后，有可能不合法，需要调整，调整过程中月份可能不合法，因此月份也要进行调整，月份调整到了13，年数就要加1
			举个例子
			2020.12.1 + 128
			2020.12.129   129>31
			2020.13.98    13>12
			2021.1.98     98>31
			2021.2.67     67>28
			2021.3.39     39>31
			2021.4.8      1<8<31   合法
			*/
			while (day>GetMonthDay(year, month))
			{
				day -= GetMonthDay(year, month);
				month++;
				if (month > 12)
				{
					month = 1;
					year++;
				}
			}
		}
		return *this;
	}
	Date operator+(int day1) const //上面的+=函数和这个+函数的区别是，上面的对象的参数发生了改变，而这个对象本身并不变
	{
		Date tmp(*this); //拷贝构造tmp用于返回，因为this本身是不会改变的，这就是+=和+的区别
		tmp += day1;
		return tmp;
	}
	Date operator-(int day1)
	{
		Date tmp(*this);
		tmp -= day1;
		return tmp;
	}
	Date& operator-=(int day1)
	{
		if (day1 < 0)
		{
			*this += -day1;
		}
		else
		{
			day -= day1;

			/*
			2020.2.10 - 80  day每减一次，month就跟着减一次
			2020.1.-70   -70<=0  -70+31
			2020.0.-39    0<1
			2019.12.-39  -39<=0  -39+31
			2019.11.-8   -8<=0   -8+30
			2019.11.22
			*/
			while (day <= 0)
			{
				month--;
				if (month < 1)
				{
					month = 12;
					year--;
				}
				day += GetMonthDay(year, month);
			}
		}
		return *this;
	}
	Date& operator++()    //前置++
	{
		*this += 1;
		return *this;
	}
	Date operator++(int)  //后置++
	{
		Date tmp(*this);
		*this += 1;
		return tmp;
	}
	Date& operator--()    // 前置--
	{
		*this -= 1;
		return *this;
	}
	Date operator--(int)  // 后置--
	{
		Date tmp(*this);
		*this -= 1;
		return tmp;
	}
	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;
	}
	inline bool operator >= (const Date& d)
	{
		//满足大于或者等于其中之一即可
		return *this > d || *this == d;
	}
	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 *this < d || *this == d;
	}
	bool operator != (const Date& d)
	{
		return !(*this == d);
	}
	int operator-(const Date& d) //两日期相减所差天数
	{
		Date max = *this;
		Date min = d;
		int flag = 1; //若*this>d,相减结果为正,flag=1,反之为负,flag=-1
		if (*this < d)
		{
			max = d;
			min = *this;
			flag = -1;
		}
		int n = 0;
		while (min < max)
		{
			min++;
			n++;
		}
		return n*flag;
	}
	void display()
	{
		cout << year << "年" << month << "月" << day << "日" << endl;
	}
private:
	int year;
	int month;
	int day;
};
int main()
{

	return 0;
}