The _gmtime64_s() and asctime_s() function C examples



Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Target platform: none, just for learning

Header file: Standard and Windows

Additional library: Windows Platform SDK

Additional project setting: Set project to be compiled as C

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C Code (/TC)

Other info: non-CLR or unmanaged

To do: Converting the coordinated universal time to ascii string

To show: Using the _gmtime64_s() and asctime_s() C functions





// _gmtime64_s(): This program uses _gmtime64_s() to convert a 64-bit

// integer representation of coordinated universal time to a structure named newtime, then uses asctime_s() to convert this structure to an output string.

#include <time.h>

#include <stdio.h>


int main(void)


struct tm newtime;

__int64 ltime;

char buf[26];

errno_t err;




// Obtain coordinated universal time:

err = _gmtime64_s(&newtime, &ltime);

if (err)


printf("Invalid Argument to _gmtime64_s().");



// Convert to an ASCII representation

err = asctime_s(buf, 26, &newtime);

if (err)


printf("Invalid Argument to asctime_s().");


printf("Coordinated universal time is %s\n", buf);



Output example:


Coordinated universal time is Sun Dec 17 09:11:33 2006

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