指定日前的前后n天问题

问题描述：给定日期，求距离n天的前后日期

int month(int y, int m)
{
	if (m==1 || m==3 || m==5 || m==7 || m==8 || m==10 || m==12)
		return 31;
	if (m==4 || m==6 || m==9 || m==11)
		return 30;
	if (y%4==0 && y%100!=0 || y%400==0)
		return 29;
	return 28;
}

int main()
{
	int nowyear=2010;
	int nowmouth=8;
	int nowday=17;
	int num;
	cin>>num;
	for(int i=0;i<num;i++)
	{
		long long ge;
		cin>>ge;
		long long ge1=ge;
		int year=nowyear,mouth=nowmouth,day=nowday;

		while(ge1>0)
		{
			ge1--;
			day++;
			if(day==(month(year,mouth)+1))
			{
				day=1;
				mouth++;
				if(mouth==13)
				{
					year++;
					mouth=1;
				}
			}
		}

		cout<<year<<"/";
		if(mouth<10)
			cout<<"0";
		cout<<mouth<<"/";
		if(day<10)
			cout<<"0";
		cout<<day;
		cout<<" ";
		long long ge2=ge;
		year=nowyear;
		mouth=nowmouth;
		day=nowday;

		while(ge2>0)
		{
			ge2--;
			day--;
			if(day==0)
			{
				mouth--;
				if(mouth==0)
				{
					year--;
					if(year==0)
						year--;
					mouth=12;
				}
				day=month(year, mouth);
			}

		}
		cout<<year<<"/";
		if(mouth<10)
			cout<<"0";
		cout<<mouth<<"/";
		if(day<10)
			cout<<"0";
		cout<<day;
		cout<<endl;
	}
}