std::chrono::year_month
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header  <chrono>
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|   class year_month;  | 
(since C++20) | |
The class year_month represents a specific month of a specific year, but with an unspecified day. It is a field-based time point, with a resolution of std::chrono::months.
year_month is a TriviallyCopyable StandardLayoutType.
Member functions
  constructs a year_month (public member function)  | |
|   accesses the stored year and month  (public member function)  | |
  modifies the year_month by some number of months or years (public member function)  | |
   checks if this year_month is valid  (public member function)  | 
Nonmember functions
   compares two year_month objects  (function)  | |
  performs arithmetic on year_month (function)  | |
   outputs a year_month into a stream  (function template)  | |
   outputs a year_month into a stream according to the provided format  (function template)  | |
   parses a year_month from a stream according to the provided format   (function template)  |