std::chrono::duration::zero
From cppreference.com
                    
                                        
                    
                    
                                                            
                    | static constexpr duration zero(); | ||
Returns a zero-length duration.
If the representation rep of the duration requires some other implementation to return a zero-length duration, std::chrono::duration_values can be specialized to return the desired value.
Parameters
(none)
Return value
returns std::chrono::duration(std::chrono::duration_values<rep>::zero())
See also
| [static] | returns the special duration value min (public static member function) | 
| [static] | returns the special duration value max (public static member function) |