26 Time library [time]

26.8 The civil calendar [time.cal]

26.8.5 Class year [time.cal.year]

26.8.5.1 Overview [time.cal.year.overview]

namespace std::chrono {
  class year {
    short y_;                   // exposition only
  public:
    year() = default;
    constexpr explicit year(int y) noexcept;

    constexpr year& operator++()    noexcept;
    constexpr year  operator++(int) noexcept;
    constexpr year& operator--()    noexcept;
    constexpr year  operator--(int) noexcept;

    constexpr year& operator+=(const years& y) noexcept;
    constexpr year& operator-=(const years& y) noexcept;

    constexpr year operator+() const noexcept;
    constexpr year operator-() const noexcept;

    constexpr bool is_leap() const noexcept;

    constexpr explicit operator int() const noexcept;
    constexpr bool ok() const noexcept;

    static constexpr year min() noexcept;
    static constexpr year max() noexcept;
  };
}
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 is Cpp17EqualityComparable (Table 23) and Cpp17LessThanComparable (Table 24), and participates in basic arithmetic with years objects, which represent a difference between two year objects.
year is a trivially copyable and standard-layout class type.