Help with errors

[Memory7]

Write your question here.
I am getting these errors
Error 2 error LNK1120: 1 unresolved externals c:\users\ira\documents\visual studio 2013\Projects\ConsoleApplication117\Debug\ConsoleApplication117.exe 1 1 ConsoleApplication117

and

Error 1 error LNK2019: unresolved external symbol "public: __thiscall Date::Date(int,int,int)" (??0Date@@QAE@HHH@Z) referenced in function _main c:\Users\Ira\documents\visual studio 2013\Projects\ConsoleApplication117\ConsoleApplication117\3.obj ConsoleApplication117


here is the code I am trying to run

#include <iostream>
using namespace std;

class Date
{
int month;
int day;
int year;

Date();
void showDate1();
void showDate2();
void showDate3();
void setDate(int newM, int newD, int newY);

};

#include <iostream>
#include <string>
using namespace std;
#include "Date.h"

Date::Date()
{
month = 1;
day = 1;
year = 2001;
}
void Date::setDate(int newM, int newD, int newY)
{
month = newM;
day = newD;
year = newY;

}

string monthName[] = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };

void Date::showDate1()
{
cout << month << "/" << day << "/" << year << endl;
}

void Date::showDate2()
{
cout << monthName[month] << " " << day << ", " << year << endl;
}
void Date::showDate3()
{
cout << day << " " << monthName[month] << " " << year << endl;
}


#include <iostream>
using namespace std;
#include "Date.h"
int main()
{
Date d1;
Date d2(2, 12, 2010);
d1.showDate1();
d2.showDate2();
d1.setDate(8, 29, 1986);
d1.showDate3();
system("pause");
return 0;
}


any help is appreciated. Thanks

[Memory7]

using Visual studios

[MiiNiPaa]

Date d2(2, 12, 2010); Show definition of three-variable constructor in your code.