29 Time library [time]

29.8 The civil calendar [time.cal]

29.8.16 Class year_month_weekday [time.cal.ymwd]

29.8.16.1 Overview [time.cal.ymwd.overview]

namespace std::chrono { class year_month_weekday { chrono::year y_; // exposition only chrono::month m_; // exposition only chrono::weekday_indexed wdi_; // exposition only public: year_month_weekday() = default; constexpr year_month_weekday(const chrono::year& y, const chrono::month& m, const chrono::weekday_indexed& wdi) noexcept; constexpr year_month_weekday(const sys_days& dp) noexcept; constexpr explicit year_month_weekday(const local_days& dp) noexcept; constexpr year_month_weekday& operator+=(const months& m) noexcept; constexpr year_month_weekday& operator-=(const months& m) noexcept; constexpr year_month_weekday& operator+=(const years& y) noexcept; constexpr year_month_weekday& operator-=(const years& y) noexcept; constexpr chrono::year year() const noexcept; constexpr chrono::month month() const noexcept; constexpr chrono::weekday weekday() const noexcept; constexpr unsigned index() const noexcept; constexpr chrono::weekday_indexed weekday_indexed() const noexcept; constexpr operator sys_days() const noexcept; constexpr explicit operator local_days() const noexcept; constexpr bool ok() const noexcept; }; }
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year_month_weekday represents a specific year, month, and weekday of the month.
year_month_weekday is a field-based time point with a resolution of days.
[Note 1: 
year_month_weekday 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 meets the Cpp17EqualityComparable (Table 28) requirements.
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year_month_weekday is a trivially copyable and standard-layout class type.

29.8.16.2 Member functions [time.cal.ymwd.members]

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constexpr year_month_weekday(const chrono::year& y, const chrono::month& m, const chrono::weekday_indexed& wdi) noexcept;
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Effects: Initializes y_ with y, m_ with m, and wdi_ with wdi.
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constexpr year_month_weekday(const sys_days& dp) noexcept;
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Effects: Constructs an object of type year_month_weekday which corresponds to the date represented by dp.
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Remarks: For any value ymwd of type year_month_weekday for which ymwd.ok() is true, ymwd == year_month_weekday{sys_days{ymwd}} is true.
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constexpr explicit year_month_weekday(const local_days& dp) noexcept;
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Effects: Equivalent to constructing with sys_days{dp.time_since_epoch()}.
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constexpr year_month_weekday& operator+=(const months& m) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Effects: *this = *this + m.
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Returns: *this.
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constexpr year_month_weekday& operator-=(const months& m) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Effects: *this = *this - m.
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Returns: *this.
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constexpr year_month_weekday& operator+=(const years& y) noexcept;
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Effects: *this = *this + y.
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Returns: *this.
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constexpr year_month_weekday& operator-=(const years& y) noexcept;
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Effects: *this = *this - y.
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Returns: *this.
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constexpr chrono::year year() const noexcept;
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Returns: y_.
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constexpr chrono::month month() const noexcept;
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Returns: m_.
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constexpr chrono::weekday weekday() const noexcept;
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Returns: wdi_.weekday().
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constexpr unsigned index() const noexcept;
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Returns: wdi_.index().
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constexpr chrono::weekday_indexed weekday_indexed() const noexcept;
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Returns: wdi_.
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constexpr operator sys_days() const noexcept;
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Returns: If y_.ok() && m_.ok() && wdi_.weekday().ok(), returns a sys_days that represents the date (index() - 1) * 7 days after the first weekday() of year()/month().
If index() is 0 the returned sys_days represents the date 7 days prior to the first weekday() of year()/month().
Otherwise the returned value is unspecified.
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constexpr explicit operator local_days() const noexcept;
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Returns: local_days{sys_days{*this}.time_since_epoch()}.
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constexpr bool ok() const noexcept;
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Returns: If any of y_.ok(), m_.ok(), or wdi_.ok() is false, returns false.
Otherwise, if *this represents a valid date, returns true.
Otherwise, returns false.

29.8.16.3 Non-member functions [time.cal.ymwd.nonmembers]

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constexpr bool operator==(const year_month_weekday& x, const year_month_weekday& y) noexcept;
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Returns: x.year() == y.year() && x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed()
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constexpr year_month_weekday operator+(const year_month_weekday& ymwd, const months& dm) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed().
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constexpr year_month_weekday operator+(const months& dm, const year_month_weekday& ymwd) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: ymwd + dm.
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constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const months& dm) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: ymwd + (-dm).
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constexpr year_month_weekday operator+(const year_month_weekday& ymwd, const years& dy) noexcept;
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Returns: {ymwd.year()+dy, ymwd.month(), ymwd.weekday_indexed()}.
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constexpr year_month_weekday operator+(const years& dy, const year_month_weekday& ymwd) noexcept;
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Returns: ymwd + dy.
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constexpr year_month_weekday operator-(const year_month_weekday& ymwd, const years& dy) noexcept;
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Returns: ymwd + (-dy).
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template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const year_month_weekday& ymwd);
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Effects: Equivalent to: return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{}/{:L}/{:L}"), ymwd.year(), ymwd.month(), ymwd.weekday_indexed());