std::chrono::weekday::ok (3) Linux Manual Page

std::chrono::weekday::ok – std::chrono::weekday::ok

Synopsis

constexpr bool ok() const noexcept; (since C++20)
Checks if the weekday value stored in *this is in the valid range, i.e., [0, 6].

Return value

true if the weekday value stored in *this is in the range [0, 6]. Otherwise false.