std::chrono...th_day_last(3)

okay bestie, welcome to the std::chrono...th_day_last(3) page from the C++ Standard Libary manual ✨ this one is all about the very last day of a month, and it’s lowkey iconic 💅

💖 NAME 💖

std::chrono::year_month_day_last — std::chrono::year_month_day_last. That’s the name, bestie, no cap 🎀

🌸 Synopsis 🌸

Defined in header <chrono> ✨

class year_month_day_last;  (since C++20)

The class year_month_day_last represents the last day of a specific year and month. It’s a field-based time point, with a resolution of std::chrono::days, subject to the limit that it can only represent the last day of a month 🗓️

std::chrono::years- and std::chrono::months-oriented arithmetic are supported directly. An implicit conversion to std::chrono::sys_days allows std::chrono::days-oriented arithmetic to be performed efficiently ⚡

year_month_day_last is a TriviallyCopyable StandardLayoutType. Slay 💅

lowkey important vibe check: it can only represent the last day of a month. That’s its whole main-character thing 🌙

🛠️ Member functions 🛠️

• constructor — constructs a year_month_day_last object (public member function)
• operator+= — modifies the time point by some number of months or years (public member function)
• operator-= — (public member function), listed as the minus-equals companion to operator+=
• year, month — accesses the fields of this object
• day — accesses the fields of this object (public member function)
• month_day_last — accesses the fields of this object
• operator sys_days — converts to a std::chrono::time_point
• operator local_days — the local-days conversion operator (public member function)
• ok — checks whether this object represents a valid date (public member function)

🦋 Nonmember functions 🦋

• operator== — compares two year_month_day_last values
• operator<=> — the spaceship comparison, marked (C++20) (function)
• operator+ / operator- — adds or subtracts a year_month_day_last and some number of years or months, marked (C++20) (function)
• operator<< — outputs a year_month_day_last into a stream, marked (C++20) (function template)

🌈 Helper classes 🌈

• std::formatter<std::chrono::year_month_day_last> — formatting support for year_month_day_last, marked (C++20) (class template specialization)
• std::hash<std::chrono::year_month_day_last> — hash support for std::chrono::year_month_day_last, marked (C++26) (class template specialization)

💻 Example 💻

// Run this code

#include <chrono>
#include <iostream>

int main()
{
    const auto ymd = std::chrono::year_month_day
    {
        std::chrono::floor<std::chrono::days>(std::chrono::system_clock::now())
    };

    const std::chrono::year_month_day_last ymdl
    {
        ymd.year(), ymd.month() / std::chrono::last
    };

    std::cout << "The last day of present month (" << ymdl << ") is: "
              << std::chrono::year_month_day{ymdl}.day() << '\n';

    // The 'last' object can be placed wherever it is legal to place a 'day':
    using namespace std::chrono;
    constexpr std::chrono::year_month_day_last
        ymdl1 = 2023y / February / last,
        ymdl2 = last / February / 2023y,
        ymdl3 = February / last / 2023y;
    static_assert(ymdl1 == ymdl2 && ymdl2 == ymdl3);
}

🌟 Possible output: 🌟

The last day of present month (2023/Aug/last) is: 31

👀 See also 👀

• year_month_day — represents a specific year, month, and day, marked (C++20) (class)

okay that’s the whole std::chrono...th_day_last(3) manual page, bestie! Source: http://cppreference.com, version date: 2024.06.10. Go slay your last-day-of-month era 💅✨🫶