std:: asctime

Converts given calendar time std::tm to a textual representation of the following fixed 25-character form: Www Mmm dd hh : mm : ss yyyy\n .

• Www - three-letter English abbreviated day of the week from time_ptr - > tm_wday , one of Mon , Tue , Wed , Thu , Fri , Sat , Sun .
• Mmm - three-letter English abbreviated month name from time_ptr - > tm_mon , one of Jan , Feb , Mar , Apr , May , Jun , Jul , Aug , Sep , Oct , Nov , Dec .
• dd - 2-digit day of the month from timeptr - > tm_mday as if printed by sprintf using % 2d .
• hh - 2-digit hour from timeptr - > tm_hour as if printed by sprintf using % .2d .
• mm - 2-digit minute from timeptr - > tm_min as if printed by sprintf using % .2d .
• ss - 2-digit second from timeptr - > tm_sec as if printed by sprintf using % .2d .
• yyyy - 4-digit year from timeptr - > tm_year + 1900 as if printed by sprintf using % 4d .

The behavior is undefined if any member of * time_ptr is outside its normal range.

The behavior is undefined if the calendar year indicated by time_ptr - > tm_year has more than 4 digits or is less than the year 1000.

The function does not support localization, and the newline character cannot be removed.

The function modifies static storage and is not thread-safe.

Parameters

Return value

Pointer to a static null-terminated character string holding the textual representation of date and time. The string may be shared between std::asctime and std::ctime , and may be overwritten on each invocation of any of those functions.

Notes

This function returns a pointer to static data and is not thread-safe. POSIX marks this function obsolete and recommends locale-dependent std::strftime instead. In std::locale ("C") the std::strftime format string "%c \n " will be an exact match to std::asctime output, while in other locales the format string "%a %b %e %H:%M:%S %Y \n " will be a potentially closer but not always exact match.

POSIX limits undefined behaviors only to the cases when the output string would be longer than 25 characters, when timeptr->tm_wday or timeptr->tm_mon are not within the expected ranges, or when timeptr->tm_year exceeds INT_MAX - 1990 .

Some implementations handle timeptr - > tm_mday == 0 as meaning the last day of the preceding month.

Example

#include <ctime>
#include <iomanip>
#include <iostream>
 
int main()
{
    const std::time_t now = std::time(nullptr);
 
    for (const char* localeName : {"C", "en_US.utf8", "de_DE.utf8", "ja_JP.utf8"})
    {
        std::cout << "locale " << localeName << ":\n" << std::left;
        std::locale::global(std::locale(localeName));
 
        std::cout << std::setw(40) << "    asctime" << std::asctime(std::localtime(&now));
 
        // strftime output for comparison:
        char buf[64];
        if (strftime(buf, sizeof buf, "%c\n", std::localtime(&now)))
            std::cout << std::setw(40) << "    strftime %c" << buf;
 
        if (strftime(buf, sizeof buf, "%a %b %e %H:%M:%S %Y\n", std::localtime(&now)))
            std::cout << std::setw(40) << "    strftime %a %b %e %H:%M:%S %Y" << buf;
 
        std::cout << '\n';
    }
}

locale C:
    asctime                             Wed Nov  4 00:45:01 2020
    strftime %c                         Wed Nov  4 00:45:01 2020
    strftime %a %b %e %H:%M:%S %Y       Wed Nov  4 00:45:01 2020
 
locale en_US.utf8:
    asctime                             Wed Nov  4 00:45:01 2020
    strftime %c                         Wed 04 Nov 2020 12:45:01 AM UTC
    strftime %a %b %e %H:%M:%S %Y       Wed Nov  4 00:45:01 2020
 
locale de_DE.utf8:
    asctime                             Wed Nov  4 00:45:01 2020
    strftime %c                         Mi 04 Nov 2020 00:45:01 UTC
    strftime %a %b %e %H:%M:%S %Y       Mi Nov  4 00:45:01 2020
 
locale ja_JP.utf8:
    asctime                             Wed Nov  4 00:45:01 2020
    strftime %c                         2020年11月04日 00時45分01秒
    strftime %a %b %e %H:%M:%S %Y       水 11月  4 00:45:01 2020

See also