this program calculates the difference between two dates implemented in c++

datediff.cpp

#include <iostream>

using namespace std;

int main()
{
    //initializations
    int dd2,mm2,yyyy2;
    int dd1,mm1,yyyy1;
    int dd,mm,yyyy;
    //inputs
    cout<<"enter current date format dd mm yyyy"<<endl;
    cin>>dd2>>mm2>>yyyy2;
    cout<<"enter birth date format dd mm yyyy"<<endl;
    cin>>dd1>>mm1>>yyyy1;

    //verify
    cout<<"current date is "<<dd2<<"/"<<mm2<<"/"<<yyyy2<<endl;
    cout<<"birth date is "<<dd1<<"/"<<mm1<<"/"<<yyyy1<<endl;

    //calc
    yyyy=yyyy2-yyyy1;
    mm=mm2-mm1;
    dd=dd2-dd1;

    //case if dd is negative i.e. current dd is less than birth date
    if(dd<0)
    {
       mm--;
       dd+=30;
    }

    //case if mm is negative i.e. current mm is less than birth  date
    if (mm<0)
    {
        yyyy--;
        mm+=12;
    }

    //final output
    cout<<"Difference between dates is "<<dd<<" days "<<mm<<" months and "<<yyyy<<" years"<<endl;
    return 0;
}

And how can we calculate actual Number of days when there is a leap year