< cpp‎ | chrono‎ | c
Utilities library
Language support
Type support (basic types, RTTI)
Library feature-test macros (C++20)
Dynamic memory management
Program utilities
Coroutine support (C++20)
Variadic functions
Debugging support
Three-way comparison
General utilities
Date and time
Function objects
Formatting library (C++20)
Relational operators (deprecated in C++20)
Integer comparison functions
Swap and type operations
Common vocabulary types
Elementary string conversions

Defined in header <ctime>
struct tm;

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


[edit] Member objects

int tm_sec
seconds after the minute – [061](until C++11) [060](since C++11)[note 1]
(public member object)
int tm_min
minutes after the hour – [059]
(public member object)
int tm_hour
hours since midnight – [023]
(public member object)
int tm_mday
day of the month – [131]
(public member object)
int tm_mon
months since January – [011]
(public member object)
int tm_year
years since 1900
(public member object)
int tm_wday
days since Sunday – [06]
(public member object)
int tm_yday
days since January 1 – [0365]
(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)
[edit] 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 [061] was a defect introduced in C89 and corrected in C99).

[edit] Example

#include <ctime>
#include <iostream>
int main()
    std::tm tm{};
    tm.tm_year = 2022 - 1900;
    tm.tm_mday = 1;
    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';

Possible output:

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

[edit] See also

converts time since epoch to calendar time expressed as local time
(function) [edit]
converts time since epoch to calendar time expressed as Universal Coordinated Time
(function) [edit]