constexpr bool operator==(const year_month_day& x, const year_month_day& y) noexcept;
constexpr strong_ordering operator<=>(const year_month_day& x, const year_month_day& y) noexcept;
if (auto c = x.year() <=> y.year(); c != 0) return c; if (auto c = x.month() <=> y.month(); c != 0) return c; return x.day() <=> y.day();
constexpr year_month_day operator+(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator+(const months& dm, const year_month_day& ymd) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const months& dm) noexcept;
constexpr year_month_day operator+(const year_month_day& ymd, const years& dy) noexcept;
constexpr year_month_day operator+(const years& dy, const year_month_day& ymd) noexcept;
constexpr year_month_day operator-(const year_month_day& ymd, const years& dy) noexcept;
template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, const year_month_day& ymd);
return os << (ymd.ok() ? format(STATICALLY-WIDEN<charT>("{:%F}"), ymd) : format(STATICALLY-WIDEN<charT>("{:%F} is not a valid date"), ymd));
template<class charT, class traits, class Alloc = allocator<charT>>
basic_istream<charT, traits>&
from_stream(basic_istream<charT, traits>& is, const charT* fmt,
year_month_day& ymd, basic_string<charT, traits, Alloc>* abbrev = nullptr,
minutes* offset = nullptr);