Lære Introduction to <chrono> | The <chrono> Library

Definition

In the <chrono> library, the three core concepts are duration, time_point, and clock.

A duration represents a span of time, such as 10 seconds or 5 minutes;
A time_point represents a specific point in time, relative to a clock's epoch;
A clock is a source of time, providing functions to get the current time point.

The <chrono> library was introduced in C++11 to address the limitations and lack of type safety in C-style time handling. Unlike the traditional <ctime> approach, which often uses plain integers and can be error-prone when converting between units, <chrono> provides a modern, type-safe, and flexible framework for dealing with time. Its design ensures that you cannot accidentally mix incompatible time units, and it offers higher precision by allowing you to specify different time representations. This makes <chrono> an essential tool for robust and clear time calculations in C++ programs.

main.cpp


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#include <iostream>
#include <chrono>

int main()
{
    // Declare a duration of 10 seconds
    std::chrono::duration<int> ten_seconds(10);
    std::cout << "Duration: " << ten_seconds.count() << " seconds\n";
}

The std::chrono::duration template represents a span of time. It takes two template parameters: the representation type (such as int or double) and the period (which specifies the unit, such as seconds or milliseconds). The period is typically provided as a ratio, like std::ratio<1> for seconds. This flexibility allows you to represent durations with different precisions and units.

main.cpp


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#include <iostream>
#include <chrono>

int main()
{
    // Get the current time_point from the system clock
    std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
    std::time_t now_c = std::chrono::system_clock::to_time_t(now);
    std::cout << "Current time (epoch seconds): " << now_c << "\n";
}

A std::chrono::time_point represents a specific moment in time, expressed relative to the epoch of a given clock. For example, std::chrono::system_clock::now() returns a time_point corresponding to the current time according to the system clock. This abstraction allows you to perform precise and type-safe calculations with points in time, such as measuring the interval between two events.

Note

<chrono> types are strongly typed, so you cannot accidentally mix durations of different units (such as seconds and milliseconds) without explicit conversions. This reduces errors and makes your code safer when working with time-related calculations.

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Definition

In the <chrono> library, the three core concepts are duration, time_point, and clock.

A duration represents a span of time, such as 10 seconds or 5 minutes;
A time_point represents a specific point in time, relative to a clock's epoch;
A clock is a source of time, providing functions to get the current time point.

main.cpp


              123456789
            
#include <iostream>
#include <chrono>

int main()
{
    // Declare a duration of 10 seconds
    std::chrono::duration<int> ten_seconds(10);
    std::cout << "Duration: " << ten_seconds.count() << " seconds\n";
}

main.cpp


              12345678910
            
#include <iostream>
#include <chrono>

int main()
{
    // Get the current time_point from the system clock
    std::chrono::time_point<std::chrono::system_clock> now = std::chrono::system_clock::now();
    std::time_t now_c = std::chrono::system_clock::to_time_t(now);
    std::cout << "Current time (epoch seconds): " << now_c << "\n";
}

Note

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