std::chrono::time_point<Clock,Duration>::operator++, std::chrono::time_point<Clock,Duration>::operator--
From cppreference.com
                    
                                        
                    < cpp | chrono | time point
                    
                                                            
                    |   constexpr time_point& operator++();  | 
(1) | (since C++20) | 
|   constexpr time_point operator++( int );  | 
(2) | (since C++20) | 
|   constexpr time_point& operator--();  | 
(3) | (since C++20) | 
|   constexpr time_point operator--( int );  | 
(4) | (since C++20) | 
Modifies the point in time *this represents by one tick of the duration.
If d_ is a member variable holding the duration (i.e., time since epoch) of this time_point object, 
1) Equivalent to ++d_; return *this;.
2) Equivalent to return time_point(d_++).
3) Equivalent to --d_; return *this;.
4) Equivalent to return time_point(d_--);.
Parameters
(none)
Return value
1,3) A reference to this 
time_point after modification.2,4) A copy of the 
time_point made before modification.Example
| This section is incomplete Reason: no example  | 
See also
|   increments or decrements the tick count  (public member function of std::chrono::duration<Rep,Period>)  | |
|   modifies the time point by the given duration  (public member function)  | |
|    (C++11)  | 
  performs add and subtract operations involving a time point  (function template)  |