namespace std::chrono {
  class weekday_last {
    chrono::weekday wd_;                
    public:
    constexpr explicit weekday_last(const chrono::weekday& wd) noexcept;
    constexpr chrono::weekday weekday() const noexcept;
    constexpr bool ok() const noexcept;
  };
}
weekday_last represents the last weekday of a month
. [
Note 1: 
A 
weekday_last object
can be constructed by indexing a 
weekday with 
last. — 
end note]
[
Example 1: 
constexpr auto wdl = Sunday[last];      
static_assert(wdl.weekday() == Sunday);
 — 
end example]
weekday_last is a trivially copyable and standard-layout class type
.