lst-0059-book.cpp
// https://godbolt.org/z/q1znGWb85
#include <iostream>
#include <chrono>
int main() {
using namespace std::chrono;
time_point<system_clock, seconds> t1{10000s};
time_point<system_clock, seconds> t2{50000s};
auto dur = t2 - t1;
std::cout << duration_cast<hours>(dur).count() << "h"; // Output: 11h
}