Failed to use namespace correctly in my .cpp file - c++

Question

I declare a namespace MYTIME in mytime.h file.
#include<ostream>
#ifndef _TIME_H
#define _TIME_H
namespace MYTIME{
class time
{
...
};
}
#endif
And try to use it in my time.cpp file,
#include"mytime.h"
#include<iostream>
using namespace std;
using namespace MYTIME;
time::time()
{
years = days = hours = minutes = 0;
seconds = 0;
months = JAN;
}
when I use g++ time.cpp to compile, errors are as follows
time.cpp:8:17: error: ‘MYTIME’ is not a namespace-name
using namespace MYTIME;
^~~~~~
time.cpp:8:23: error: expected namespace-name before ‘;’ token
using namespace MYTIME;
^
time.cpp:10:1: error: ‘time’ does not name a type
time::time()
time.cpp:31:6: error: ‘time’ is not a class, namespace, or enumeration
void time::addSec(long int s)
time.cpp: In function ‘void addSec(long int)’:
time.cpp:34:7: error: ‘seconds’ was not declared in this scope
m = (seconds + s) / 60;
^~~~~~~
time.cpp:34:7: note: suggested alternative: ‘useconds_t’
m = (seconds + s) / 60;
^~~~~~~
useconds_t
... // many same errors
where am i going wrong? and how to fix it? Looking for help.

Answer 1

Your header guard is using a name that is already defined. As a result, your namespace and class is never declared.
A simple test demonstrates the problem:
#include <iostream>
int main()
{
#ifdef _TIME_H
std::cout << "Well, well, well...\n";
#endif
}
You would expect this program to have no output, but when compiled with g++ and run, this program outputs:
Well, well, well...
To solve this, you should use more uniquely named headers, and don't attempt to use naming conventions employed by the standard library. In particular, prefixing with an underscore is generally not a good idea.
If your compiler supports #pragma once you may wish to consider using that instead.