##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::chrono::system_clock::now

From cppreference.com
< cpp‎ | chrono‎ | system clock

[edit template]

static std::chrono::time_point<std::chrono::system_clock> now(); |  | (since C++11)

Returns a time point representing the current point in time.

### [edit] Parameters

(none)

### [edit] Return value

A time point representing the current time.

### [edit] Exceptions

`noexcept` specification:
noexcept

### [edit] Example

Run this code

    #include <iostream>
    #include <vector>
    #include <numeric>
    #include <chrono>

    volatile int sink;
    int main()
    {
        for (auto size = 1ull; size < 1000000000ull; size *= 100) {
            // record start time
            auto start = std::chrono::system_clock::now();
            // do some work
            std::vector<int> v(size, 42);
            sink = std::accumulate(v.begin(), v.end(), 0u); // make sure it's a side effect
            // record end time
            auto end = std::chrono::system_clock::now();
            std::chrono::duration<double> diff = end-start;
            std::cout << "Time to fill and iterate a vector of "
                      << size << " ints : " << diff.count() << " s\n";
        }
    }

Possible output:

    Time to fill and iterate a vector of 1 ints : 2.43e-07 s
    Time to fill and iterate a vector of 100 ints : 4.1e-07 s
    Time to fill and iterate a vector of 10000 ints : 2.519e-05 s
    Time to fill and iterate a vector of 1000000 ints : 0.00207669 s
    Time to fill and iterate a vector of 100000000 ints : 0.423087 s

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/chrono/system_clock/now&oldid=50431"
Category:

- unconditionally noexcept

Hidden categories:

- Pages with unreviewed unconditional noexcept template
- Pages with unreviewed noexcept template