C++20 changes to std::chrono you might not be aware of: clocks and more

C++20 extended std::chrono beyond calendar and time zone support by introducing five new clock types: utc_clock, tai_clock, gps_clock, file_clock, and local_t. Each serves a distinct purpose — UTC time, international atomic time, GPS time, filesystem time, and local time representation respectively. C++20 also added helper utilities including is_clock, clock_cast, and the clock_time_conversion trait, enabling conversion of time_points between different clock types.