std::tm(3)

✨ NAME ✨

std::tm — std::tm (yes bestie, that's the whole name, no cap). This is the std::tm(3) page from the C++ Standard Libary, and it's all about std::tm: a structure holding a calendar date and time broken down into its components. 💖

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🌸 Synopsis 🌸

Defined in header <ctime>
struct tm;

Structure holding a calendar date and time broken down into its components. 🦋

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🫶 Member objects 🫶

• int tm_sec — seconds after the minute. Range: [0, 61] (until C++11), then [0, 60] (since C++11)^[note 1]. (public member object)
• int tm_min — minutes after the hour. Range: [0, 59]. (public member object)
• int tm_hour — hours since midnight. Range: [0, 23]. (public member object)
• int tm_mday — day of the month. Range: [1, 31]. (public member object)
• int tm_mon — months since January. Range: [0, 11]. (public member object)
• int tm_year — years since 1900. (public member object)
• int tm_wday — days since Sunday. Range: [0, 6]. (public member object)
• int tm_yday — days since January 1. Range: [0, 365]. (public member object)
• int tm_isdst — Daylight Saving Time flag. The value is positive if DST is in effect, zero if not and negative if no information is available. (public member object)

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💅 Notes 💅

The Standard mandates only the presence of the aforementioned members in some order. The implementations usually add more data members to this structure. 🫶

1. ↑ Range allows for a positive leap second. Two leap seconds in the same minute are not allowed (the range [0, 61] was a defect introduced in C89 and corrected in C99).

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✨ Example ✨

This is the code, bestie — run it if you want the vibe check:

// Run this code

#include <ctime>
#include <iostream>

int main()
{
    std::tm tm{};
    tm.tm_year = 2022 - 1900;
    tm.tm_mday = 1;
    std::mktime(&tm);

    std::cout << std::asctime(&tm); // note implicit trailing '\n'

    std::cout << "sizeof(std::tm) = " << sizeof(std::tm) << '\n'
              << "sum of sizes of standard members = "
              << sizeof(tm.tm_sec) +
                 sizeof(tm.tm_min) +
                 sizeof(tm.tm_hour) +
                 sizeof(tm.tm_mday) +
                 sizeof(tm.tm_mon) +
                 sizeof(tm.tm_year) +
                 sizeof(tm.tm_wday) +
                 sizeof(tm.tm_yday) +
                 sizeof(tm.tm_isdst) << '\n';
}

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🔥 Possible output 🔥

Like, maybe your machine prints this exactly:

Sat Jan  1 00:00:00 2022
sizeof(std::tm) = 56
sum of sizes of standard members = 36

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👑 See also 👑

• localtime — converts time since epoch to calendar time expressed as local time. (function)
• gmtime — converts time since epoch to calendar time expressed as Universal Coordinated Time. (function)
• C documentation for tm — the C-side twin, iykyk. 😌

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✨ okay that's the page! source/version: http://cppreference.com; date: 2024.06.10; manual page: std::tm(3). slay and goodbye 💖💅🎀