求完善日期判断逻辑

#include<iostream.h>
class Date{
	int y,m,d;
public:
	Date(){
		y=2015;m=4;d=30;
	}
	Date(int y,int m,int d){
		this->y=y;
		this->m=m;
		this->d=d;
	}
	Date operator ++(){
		++d;
		cout<<d;
		return *this;
	}
	Date operator ++(int){
		d++;
		cout<<d;
		return *this;
	}
	void display(){
		cout<<y<<m<<d;
	}
};

void main(){
	Date d1(2015,5,2);
	d1++;
	cout<<"\n";
	++d1;
}