Objects of class system_clock represent wall clock time from the system-wide
realtime clock.

class system_clock { public: using rep = see below; using period = ratio<unspecified, unspecified>; using duration = chrono::duration<rep, period>; using time_point = chrono::time_point<system_clock>; static constexpr bool is_steady = unspecified; static time_point now() noexcept; // Map to C API static time_t to_time_t (const time_point& t) noexcept; static time_point from_time_t(time_t t) noexcept; };

```
using system_clock::rep = unspecified;
```

```
static time_t to_time_t(const time_point& t) noexcept;
```

```
static time_point from_time_t(time_t t) noexcept;
```