# std::literals::chrono_literals::operator""d

From cppreference.com
< cpp‎ | chrono

Defined in header `<chrono>` |  |
constexpr std::chrono::day operator ""d( unsigned long long d ) noexcept; |  | (since C++20)

Forms a std::chrono::day literal representing a day of the month in the calendar.

### Parameters

d | - | the day value

### Return value

A std::chrono::day storing d. If d > 255, the stored value is unspecified.

### Possible implementation

    constexpr std::chrono::day operator ""d(unsigned long long d) noexcept
    {
        return std::chrono::day(d);
    }

### Notes

This operator is declared in the namespace std::literals::chrono_literals, where both literals and chrono_literals are inline namespaces. Access to this operator can be gained with:

- using namespace std::literals,
- using namespace std::chrono_literals, or
- using namespace std::literals::chrono_literals.

In addition, within the namespace std::chrono, the directive using namespace literals::chrono_literals; is provided by the standard library, so that if a programmer uses using namespace std::chrono; to gain access to the classes in the chrono library, the corresponding literal operators become visible as well.

### Example

Run this code

    #include <chrono>
    #include <iostream>

    int main()
    {
        using namespace std::literals::chrono_literals;

        std::cout << static_cast<unsigned>(42d) << '\t' << 42d << '\n'
                  << static_cast<unsigned>(256d) << '\t' << 256d << '\n' // unspecified
                  << static_cast<unsigned>(298d) << '\t' << 298d << '\n'; // unspecified
    }

Possible output:

    42      42 is not a valid day
    0       00 is not a valid day
    42      42 is not a valid day

### See also

(constructor) | constructs a `day` (public member function of `std::chrono::day`)
operator unsigned | retrieves the stored day value (public member function of `std::chrono::day`)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/chrono/operator%22%22d&oldid=157624"