cpp/chrono/year month/operator arith 2

@1-2@ Adds years to. @3-4@ Adds months to. @5@ Subtracts years from. @6@ Subtracts months from. @7@ Returns the difference in months between the two time points represented by and.

For durations that are convertible to both std and std, the overloads  are preferred if the call would otherwise be ambiguous.

Return value
@1-2@ @3-4@ A value  such that  and. @5@ @6@ @7@