Why doesn't tie function work with const class methods?

#include <string>
#include <tuple>
#include <stdexcept>

using namespace std;

class Date {
public:
  Date() {};
  Date(int new_year, int new_month, int new_day) {
      year = new_year;

      if ( (new_month < 1) || (new_month > 12) ) {
          throw runtime_error("Month value is invalid: " + to_string(new_month));
      }
      month = new_month;

      if ( (new_day < 1) || (new_day > 31) ) {
          throw runtime_error("Day value is invalid: " + to_string(new_day));
      }
      day = new_day;
  }
  int GetYear() const {
      return year;
  }
  int GetMonth() const {
      return month;
  }
  int GetDay() const {
      return day;
  }
private:
  int year;
  int month;
  int day;
};

bool operator<(const Date& lhs, const Date& rhs) {
    auto lhs = tie(lhs.GetYear(), lhs.GetMonth(), lhs.GetDay());
    auto rhs = tie(rhs.GetYear(), rhs.GetMonth(), rhs.GetDay());

    return lhs < rhs;
}

I'm trying to create a class for storing the date (year, month, day). In order to use this class in a map, I want to overload the comparison operator. Unfortunately, the code above does not work. The compiler gives me an error

error: cannot bind non-const lvalue reference of type 'int&' to an rvalue of type 'int'|

The error apparently occurs in tie function. Once I change it to make_tuple everything compiles and works. I also checked that if I declared variables year, month and day as public I could write something like

auto lhs = tie(lhs.year, lhs.month, lhs.day);

and this would also work. I don't understand why. Does anyone have ideas?