year represents a year in the civil calendar
.  It can represent values in the range [
min(), max()]
.It can be constructed with any 
int value,
which will be subsequently truncated to fit into 
year's unspecified internal storage
.year meets the 
Cpp17EqualityComparable (Table 
28)
and 
Cpp17LessThanComparable (Table 
29) requirements,
and participates in basic arithmetic with 
years objects,
which represent a difference between two 
year objects
.