运算符重载must take either zero or one argument?

C++中运算符+重载出错

//Time.h
#ifndef TIME_H
#define TIME_H
#include<iostream>
using namespace std;

class Time
{
public:
    Time(int H=0,int M=0,int S=0);
    void SetTime(int H,int M,int S);
    Time operator+(const Time &t, int n);
    friend ostream & operator<<(ostream &out,const Time &t);
private:
    int h,m,s;
};
#endif

//Time.cpp
#include<iostream>
#include"Time.h"
using namespace std;

Time::Time(int H,int M,int S):h(H),m(M),s(S){}
void Time::SetTime(int H,int M,int S)
{
    h=H,m=M,s=S;
}

Time Time::operator+(const Time &t, int n)
{
    Time temp(t);
    int y=n+s+60*(m+60*h);
    temp.s=y%60;
    temp.m=y/60%60;
    temp.h=y/3600;
    return temp;
}

ostream & operator<<(ostream &out,const Time &t)
{
    out<<t.h<<":"<<t.m<<"."<<t.s;
    return out;
}

//Test.cpp
#include<iostream>
#include"Time.h"
using namespace std;

int main()
{
    Time t1,t2;
    t1.SetTime(23,10,29);
    t2.SetTime(10,4,23);
    cout<<t1+3;
    return 0;
}

我的理解是重载operator+，相当于timeObj1+timeObj2,如果增加了参数int n，这个表达式没办法展开，也就形成不了操作符号重载。

类内重载操作符直接写第二个操作数就行

Time operator+( int n);
//运行时是这么调用的
t1.operator+(3);
//按你原来的写法会缺变量
t1.operator+((const Time&)3, (int)???)
//类外重载需要按你原来的写法，调用方式是
operator+(t1, 3);

那如果是1+a和a+1运算不同，需要分别声明呢？？