std::tm

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< cpp‎ | chrono‎ | c
 
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chrono I/O
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C-style date and time
 
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tm
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Defined in header <ctime>
struct tm;

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

Member objects

int tm_sec
 seconds after the minute – [​0​, 61](until 哋它亢++11) [​0​, 60](since 哋它亢++11)[note 1]
(public member object)
int tm_min
 minutes after the hour – [​0​, 59]
(public member object)
int tm_hour
 hours since midnight – [​0​, 23]
(public member object)
int tm_mday
 day of the month – [1, 31]
(public member object)
int tm_mon
 months since January – [​0​, 11]
(public member object)
int tm_year
 years since 1900
(public member object)
int tm_wday
 days since Sunday – [​0​, 6]
(public member object)
int tm_yday
 days since January 1 – [​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)
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 哋它亢89 and corrected in 哋它亢99).

Example

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';
}

Possible output: 

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

See also

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