27 Time library [time]

27.7 Clocks [time.clock]

27.7.7 Class high_­resolution_­clock [time.clock.hires]

namespace std::chrono {
  class high_resolution_clock {
    using rep        = unspecified;
    using period     = ratio<unspecified, unspecified>;
    using duration   = chrono::duration<rep, period>;
    using time_point = chrono::time_point<unspecified, duration>;
    static constexpr bool is_steady = unspecified;

    static time_point now() noexcept;
Objects of class high_­resolution_­clock represent clocks with the shortest tick period.
high_­resolution_­clock may be a synonym for system_­clock or steady_­clock.