void DateAxis(TCanvas * c)
{
  c->Update();
  TGaxis* xaxis;
  float minmjd = gPad->GetUxmin();
  float maxmjd = gPad->GetUxmax();
  float dur = (maxmjd - minmjd) * 24*3600;
  xaxis = new TGaxis(gPad->GetUxmin(), gPad->GetUymax(), gPad->GetUxmax(), gPad->GetUymax(), 0, dur, 505, "t-");
  xaxis->SetLineColor(1);
  xaxis->SetLabelOffset(0.0001);  // touching axis
  xaxis->SetLabelSize(0.04);
  xaxis->SetNdivisions(3);
  xaxis->SetTimeFormat("%d.%m.%Y");
  int year, month, day, hour, min, sec;
  MJDToCalendarDate(minmjd, year, month, day, hour, min, sec);
  
  TDatime da(year,month,day,hour,min,sec);
  xaxis->SetTimeOffset(da.Convert());
  xaxis->SetTitle("Calender Date");
  xaxis->CenterTitle();
  xaxis->Draw(); 
}

  
void MJDToCalendarDate(float mjd, int & year, int & month, int & day, int & hour, int & min, int & sec)
{
  MJDToYearDay(mjd, year, day);
  
  int monthlen[12];
  monthlen[0] = 31;
  if ( ( year % 4 == 0 && year % 100 != 0) || ( year % 400 == 0 ) ) {
    monthlen[1] = 29;
  }else{
    monthlen[1] = 28;
  }
  monthlen[2] = 31;
  monthlen[3] = 30;
  monthlen[4] = 31;
  monthlen[5] = 30;
  monthlen[6] = 31;
  monthlen[7] = 31;
  monthlen[8] = 30;
  monthlen[9] = 31;
  monthlen[10] = 30;
  monthlen[11] = 31;

  int mo = 0;
  while (day > monthlen[mo]) {
    day -= monthlen[mo];
    mo++;
  }

  month = mo + 1;
  // day is set in loop

  float remains = (mjd - (int)mjd) * 24;
  hour = (int)remains;
  remains = (remains - hour) * 60;
  min = (int)remains;
  remains = (remains - min) * 60;
  sec = (int)remains;
}

void MJDToYearDay(float mjd, int & year, float & day)
{
  int intmjd = (int)mjd;  // get rid of decimal
  float yearsin = (intmjd - 45) / 365;
  if (yearsin < 0) {
    year = 1858;
    day = 319 + intmjd;
  }else{
    int leaps = (int)(yearsin + 2) / 4;
    bool leapthisyear;
    int subleaps = (int)(leaps + 14) / 25;
    int addleaps = (int)(leaps + 64) / 100;

    if ((((int)(yearsin + 2) % 4 == 0) && ((leaps + 14) % 25 != 0)) || ((leaps + 64) % 100 == 0)) leapthisyear = true;

    leaps = leaps - subleaps + addleaps;
    int days = intmjd - 45 - leaps;
    yearsin = days / 365;
    days -= yearsin * 365;
    year = 1859 + yearsin;
    day = days + 1;
    if (day == 365 && leapthisyear) day = 366;
    day = day + (mjd - intmjd);
  }
}

void MJDToYearDay(float mjd, int & year, int & day)
{
  float fday;
  MJDToYearDay(mjd, year, fday);
  day = (int)fday;
}