25 Time library [time]

25.8 The civil calendar [time.cal]

25.8.5 Class year [time.cal.year]

25.8.5.3 Non-member functions [time.cal.year.nonmembers]

constexpr bool operator==(const year& x, const year& y) noexcept;
Returns: int{x} == int{y}.
constexpr bool operator<(const year& x, const year& y) noexcept;
Returns: int{x} < int{y}.
constexpr year operator+(const year& x, const years& y) noexcept;
Returns: year{int{x} + y.count()}.
constexpr year operator+(const years& x, const year& y) noexcept;
Returns: y + x.
constexpr year operator-(const year& x, const years& y) noexcept;
Returns: x + -y.
constexpr years operator-(const year& x, const year& y) noexcept;
Returns: years{int{x} - int{y}}.
template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const year& y);
Effects: Inserts format(fmt, y) where fmt is "%Y" widened to charT.
If !y.ok(), appends with " is not a valid year".
Returns: os.
template<class charT, class traits> basic_ostream<charT, traits>& to_stream(basic_ostream<charT, traits>& os, const charT* fmt, const year& y);
Effects: Streams y into os using the format specified by the NTCTS fmt.
fmt encoding follows the rules specified in [time.format].
Returns: os.
template<class charT, class traits, class Alloc = allocator<charT>> basic_istream<charT, traits>& from_stream(basic_istream<charT, traits>& is, const charT* fmt, year& y, basic_string<charT, traits, Alloc>* abbrev = nullptr, minutes* offset = nullptr);
Effects: Attempts to parse the input stream is into the year y using the format flags given in the NTCTS fmt as specified in [time.parse].
If the parse fails to decode a valid year, is.setstate(ios_­base::failbit) shall be called and y shall not be modified.
If %Z is used and successfully parsed, that value will be assigned to *abbrev if abbrev is non-null.
If %z (or a modified variant) is used and successfully parsed, that value will be assigned to *offset if offset is non-null.
Returns: is.
constexpr year operator""y(unsigned long long y) noexcept;
Returns: year{static_­cast<int>(y)}.