27 Time library [time]

27.8 The civil calendar [time.cal]

27.8.17 Class year_­month_­weekday_­last [time.cal.ymwdlast]

27.8.17.1 Overview [time.cal.ymwdlast.overview]

namespace std::chrono {
  class year_month_weekday_last {
    chrono::year         y_;    // exposition only
    chrono::month        m_;    // exposition only
    chrono::weekday_last wdl_;  // exposition only

  public:
    constexpr year_month_weekday_last(const chrono::year& y, const chrono::month& m,
                                      const chrono::weekday_last& wdl) noexcept;

    constexpr year_month_weekday_last& operator+=(const months& m) noexcept;
    constexpr year_month_weekday_last& operator-=(const months& m) noexcept;
    constexpr year_month_weekday_last& operator+=(const years& y)  noexcept;
    constexpr year_month_weekday_last& operator-=(const years& y)  noexcept;

    constexpr chrono::year         year()         const noexcept;
    constexpr chrono::month        month()        const noexcept;
    constexpr chrono::weekday      weekday()      const noexcept;
    constexpr chrono::weekday_last weekday_last() const noexcept;

    constexpr          operator sys_days()   const noexcept;
    constexpr explicit operator local_days() const noexcept;
    constexpr bool ok() const noexcept;
  };
}
year_­month_­weekday_­last represents a specific year, month, and last weekday of the month.
year_­month_­weekday_­last is a field-based time point with a resolution of days, except that it is restricted to pointing to the last weekday of a year and month.
Note
:
year_­month_­weekday_­last supports years- and months-oriented arithmetic, but not days-oriented arithmetic.
For the latter, there is a conversion to sys_­days, which efficiently supports days-oriented arithmetic.
— end note
 ]
year_­month_­weekday_­last is Cpp17EqualityComparable (Table 23).
year_­month_­weekday_­last is a trivially copyable and standard-layout class type.

27.8.17.2 Member functions [time.cal.ymwdlast.members]

constexpr year_month_weekday_last(const chrono::year& y, const chrono::month& m, const chrono::weekday_last& wdl) noexcept;
Effects: Constructs an object of type year_­month_­weekday_­last by initializing y_­ with y, m_­ with m, and wdl_­ with wdl.
constexpr year_month_weekday_last& operator+=(const months& m) noexcept;
Effects: *this = *this + m.
Returns: *this.
constexpr year_month_weekday_last& operator-=(const months& m) noexcept;
Effects: *this = *this - m.
Returns: *this.
constexpr year_month_weekday_last& operator+=(const years& y) noexcept;
Effects: *this = *this + y.
Returns: *this.
constexpr year_month_weekday_last& operator-=(const years& y) noexcept;
Effects: *this = *this - y.
Returns: *this.
constexpr chrono::year year() const noexcept;
Returns: y_­.
constexpr chrono::month month() const noexcept;
Returns: m_­.
constexpr chrono::weekday weekday() const noexcept;
Returns: wdl_­.weekday().
constexpr chrono::weekday_last weekday_last() const noexcept;
Returns: wdl_­.
constexpr operator sys_days() const noexcept;
Returns: If ok() == true, returns a sys_­days that represents the last weekday() of year()/month().
Otherwise the returned value is unspecified.
constexpr explicit operator local_days() const noexcept;
Returns: local_­days{sys_­days{*this}.time_­since_­epoch()}.
constexpr bool ok() const noexcept;
Returns: y_­.ok() && m_­.ok() && wdl_­.ok().

27.8.17.3 Non-member functions [time.cal.ymwdlast.nonmembers]

constexpr bool operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) noexcept;
Returns:
x.year() == y.year() && x.month() == y.month() && x.weekday_last() == y.weekday_last()
constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
Returns: (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_­last().
constexpr year_month_weekday_last operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
Returns: ymwdl + dm.
constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
Returns: ymwdl + (-dm).
constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
Returns: {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_­last()}.
constexpr year_month_weekday_last operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
Returns: ymwdl + dy.
constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
Returns: ymwdl + (-dy).
template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const year_month_weekday_last& ymwdl);
Effects: Equivalent to:
return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{}/{}/{}"),
                    ymwdl.year(), ymwdl.month(), ymwdl.weekday_last());