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

std::chrono::month::ok – std::chrono::month::ok

Synopsis

constexpr bool ok() const noexcept; (since C++20)
Checks if the month value stored in *this is in the valid range, i.e., [1, 12].

Return value

true if the month value stored in *this is in the range [1, 12]. Otherwise false.