Re: What does mktime return????

["Walter H." <Walter.H@xxxxxxxxxxxxxxxxx>]

Hello,

I tried your programme on my system (other linux distribution), and got 
the same result;
even on windows the same results;

but this is interesting

# date --date="Dec 1 00:00:00 2019" +"%s"
1575154800

# date --date="Nov 30 23:59:59 2019" +"%s"
1575154799

there you have this 1 second difference;

I'd say mktime seens to be buggy ...

Walter

On 18.12.2019 15:17, Jouk Jansen wrote:
> Hi All,
>
> I'm strugling with the C-function mktime. According to the man-pages it
> returns "seconds  since  the Epoch". I tried to use this functions to get
> differnces from two date-times , but was could not interpret the result.
> When trying to get the diffrence between 30 Nov 2019 23:59:59 and 1 Dec 2019
> 00:00:00 (see code below) I expected to find 1 second difference but I find:
>     1577746799 1577833200 -86401
> As output of the sample program. (and not 1577833199 1577833200 -1)
>
> How should I read "seconds  since  the Epoch"????
> Is the output of mktime correct?
>       (I also tried 31 Nov and got the expected 1 second)
>       (should mktime not give an error for 31 Nov??)
>
>
>
>           Regards
> 	     Jouk
>
>
>
>
>
>
> Code :
>
>
> #include<stdio.h>
> #include<time.h>
>
> main()
> {
>     struct tm time_str , time_str2;
>
>     time_str.tm_sec = 59; //30 Nov 2019 23:59:59
>     time_str.tm_min = 59;
>     time_str.tm_hour = 23;
>     time_str.tm_mday = 30;
>     time_str.tm_mon = 11;
>     time_str.tm_year = 119;
>     time_str.tm_isdst = 0;
>
>     time_str2.tm_sec = 0; // 1 Dec 2019 00:00:00
>     time_str2.tm_min = 0;
>     time_str2.tm_hour = 0;
>     time_str2.tm_mday = 1;
>     time_str2.tm_mon = 12;
>     time_str2.tm_year = 119;
>     time_str2.tm_isdst = 0;
>
>     printf( "%d %d %d\n" , mktime(&time_str ) , mktime(&time_str2 ) ,
> 	   mktime(&time_str ) - mktime(&time_str2 ) );
>
> }

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