sample

#include <chrono>
#include <iostream>

using namespace std;

constexpr chrono::duration<long double, std::ratio<1> > operator "" _secs(long double in_secs)
{
   return move(chrono::duration<long double, std::ratio<1> >(in_secs));
}

int main()
{
   chrono::duration<long double, std::ratio<1> > test = 24.0_secs;
   cout << test.count() << endl;
   return 0;
}