std::chrono::day in C++ 20

Difference between cout and std::cout in C++

In C++, the <ctime> header provides the std::chrono::day class that represents a day in the given month. In this article, we will learn how to use the std::chrono::day class in C++.

std::chrono::day in C++

The std::chrono::day class was introduced in C++ 20 to represent a day in a month. It is a duration-based representation of the day in the calendar month. It allows for the precise calculations and manipulations of the dates and time durations. It is particularly useful when dealing with calendar-related operations and when precise handling of the time intervals is required.

Syntax of std::chrono::day

std::chrono::day d{day_count};

where:

day_count: An integer representing the day of the month ranging from 1 to 31.
Return Value: std::chrono::day object representing the specified day of the month.

Except for increment, equality and output operator overload, the std::chrono::day only have one member function named ok() which checks whether the value of the day object is in the valid range.

Example of std::chrono::day in C++

The following program illustrates how to use std::chrono::day in C++:

C++

// C++ Program for demonstrating the use of std::chrono::day
#include <chrono>
#include <ctime>
#include <iostream>

int main()
{
    using namespace std;
    using namespace std::chrono;

    // Get the current time as a time_point
    auto now = system_clock::now();
    auto today = floor<days>(now); // Truncate to days

    // Get the calendar date
    year_month_day ymd = year_month_day{ today };
    day d = ymd.day();

    // Output the day of the month
    cout << "Day of the month:-" << endl;
    cout << "Today: " << static_cast<unsigned>(d) << endl;
    d++;
    cout << "Tommorow: " << static_cast<unsigned>(d)
         << endl;

    return 0;
}

Output

Day of the month:-
Today: 4
Tommorow: 5

Time Complexity: O(1)
Auxiliary Space: O(1)

Explanation: The above program fetches the current date and extracts the day of the month from it using the std::chrono::day class.

Note: This program will only work in C++ 20 or above versions.

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std::chrono::day in C++ 20