confused in a returned reference

[Reddevil1003]

  class date
{
    int x,y,z;
    public:
        date(int a,int b, int c): x{a},y{b},z{c} {};

        void show()
        {
            cout<<x<<endl<<y<<endl<<z;
        }

};

const date& default_date()
{
    static const date dd(1970,1,2);
    return dd;
}


int main()
{
   date t=default_date();
   t.show();
    return 0;
}
Put the code you need help with here.

here if we instead use - const date default_date(); it gives same result that i understand, but how using reference const date& default_date() eliminates unnecessary copying if default_date() is called many times during the program. .

[helios]

Since you're assigning the return value of default_date() to an object, it makes absolutely no difference whether you return a reference or not, because assignment requires a copy.
If you did something like

for (int i = 0; i < 1000000; i++)
    //Note: You would need to make date::show() a const function to
    //be able to call it on this reference.
    default_date().show();

not copy would happen at all. You would just be calling show() on the static instance in default_date().