month represents a month of a year
.  It normally holds values in the range 1 to 12,
but may hold non-negative values outside this range
.It can be constructed with any 
unsigned value,
which will be subsequently truncated to fit into 
month's unspecified internal storage
.month meets the 
Cpp17EqualityComparable (Table 
28)
and 
Cpp17LessThanComparable (Table 
29) requirements,
and participates in basic arithmetic with 
months objects,
which represent a difference between two 
month objects
.