# std::literals::chrono_literals::operator""ms

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
constexpr std::chrono::milliseconds operator""ms( unsigned long long ms ); | (1) | (since C++14)
constexpr std::chrono::duration </*unspecified*/, std::milli > operator""ms( long double ms ); | (2) | (since C++14)

Forms a std::chrono::duration literal representing milliseconds.

1) Integer literal, returns exactly std::chrono::milliseconds (ms).
2) Floating-point literal, returns a floating-point duration equivalent to std::chrono::milliseconds.

### Parameters

ms | - | the number of milliseconds

### Return value

The std::chrono::duration literal.

### Possible implementation

    constexpr std::chrono::milliseconds operator""ms(unsigned long long ms)
    {
        return std::chrono::milliseconds(ms);
    }
    constexpr std::chrono::duration<long double, std::milli> operator""ms(long double ms)
    {
        return std::chrono::duration<long double, std::milli>(ms);
    }

### 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::chrono_literals;
        constexpr auto d1{250ms};
        constexpr std::chrono::milliseconds d2{1s};
        std::cout << d1 << " = " << d1.count() << " milliseconds\n"
                  << d2 << " = " << d2.count() << " milliseconds\n";
    }

Output:

    250ms = 250 milliseconds
    1000ms = 1000 milliseconds

### See also

(constructor) | constructs new duration (public member function of `std::chrono::duration<Rep,Period>`)

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