luis@ubuntu:~/$ nano getDate.cpp

//g++ getDate.cpp -o getDate
#include <ctime>
#include <iostream>
#include <sstream>
#include <cstdlib>
using namespace std;

string getDate()
{
    time_t t = time(NULL);
	tm* timePtr = localtime(&t);

    stringstream ss_year;
    ss_year << timePtr->tm_year+1900;
    string Year = ss_year.str();

    stringstream ss_month;
    ss_month << timePtr->tm_mon+1;
    string Month = ss_month.str();
    if(atoi(Month.c_str()) < 10)
        Month = "0"+Month;

    stringstream ss_day;
    ss_day << timePtr->tm_mday;
    string Day = ss_day.str();
    if(atoi(Day.c_str()) < 10)
        Day = "0"+Day;

    stringstream ss_hour;
    ss_hour << timePtr->tm_hour;
    string Hour = ss_hour.str();
    if(atoi(Hour.c_str()) < 10)
        Hour = "0"+Hour;

    stringstream ss_min;
    ss_min << timePtr->tm_min;
    string Min = ss_min.str();
    if(atoi(Min.c_str()) < 10)
        Min = "0"+Min;

    stringstream ss_sec;
    ss_sec << timePtr->tm_sec;
    string Sec = ss_sec.str();
    if(atoi(Sec.c_str()) < 10)
        Sec = "0"+Sec;

    string Fecha = Year+Month+Day+"_"+Hour+Min+Sec;

    return Fecha;
}

int main(int argc,char **argv)
{
    cout << getDate() << "\n";
}

luis@ubuntu:~/$ g++ getDate.cpp -o getDate

luis@ubuntu:~/$ ./getDate