std::chrono::time_of_day<Duration>::time_of_day
From cppreference.com
                    
                                        
                    < cpp | chrono | time of day
                    
                                                            
                    | time_of_day() = default; | (1) | |
| explicit constexpr time_of_day(precision since_midnight) noexcept; | (2) | |
Constructs a time_of_day object.
1) Default constructor leaves the object uninitialized.
2) Constructs a 
time_of_day object in 24 hour format corresponding to since_midnight after 00:00:00. As applicable:
- hours()returns the integral number of hours- since_midnightis after 00:00:00.
- minutes()returns the integral number of minutes- since_midnightis after- (00:00:00 + hours()).
- seconds()returns the integral number of seconds- since_midnightis after- (00:00:00 + hours() + minutes()).
- subseconds()returns the integral number of fractional seconds- since_midnightis after- (00:00:00 + hours() + minutes() + seconds()).