localtime() is showing 0 microseconds since 1970 as one hour

Asked Jun 30 '14 at 11:19

Active Jul 09 '14 at 00:40

Viewed 171 times

I have a timeval which is 0 seconds and 0 microseconds. I am therefore expecting zero hours:

//Create a timeval representing 0 microseconds since 1970 
struct timeval test;
test.tv_sec = 0;
test.tv_usec = 0;

struct tm *nowtm2;
time_t nowtime2;
nowtime2 = test.tv_sec;
nowtm2 = localtime(&nowtime2);

//This should output 0, but is outputting 1
std::cout << "h: " << nowtm2->tm_hour;

However, h keeps outputting the value 1, which I presume is because localtime() is adding an extra hour for daylight savings.

How can I prevent this extra hour being added?

UPDATE

std::cout << "d: " << nowtm2->tm_isdst << std::endl;

outputs zero

edited Jul 09 '14 at 00:40

Matt Johnson-Pint

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asked Jun 30 '14 at 11:19

user997112

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Have you checked the `tm_isdst` member of the `struct tm`? – Some programmer dude Jun 30 '14 at 11:20
Just did- outputs zero.... :s – user997112 Jun 30 '14 at 11:23
check your environment... most likely, you machine is in the CET time zone; it's definitely not daylight saving since 1.1.1970 00:00 is in winter – Erich Kitzmueller Jun 30 '14 at 11:28
@ammoQ wouldnt that add 3/4 hours, rather than just one? – user997112 Jun 30 '14 at 11:31
No, CET is GMT+1; what's the output of `echo $TZ`? – Erich Kitzmueller Jun 30 '14 at 11:31
@ammoQ I have just checked nowtm2->tm_zone and its "BST" (british summer time) which is obviously 1 away from GMT.... – user997112 Jun 30 '14 at 11:33
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Jan 1st should not fall into BST... strange... any reason why you don't use `gmtime()`? – Erich Kitzmueller Jun 30 '14 at 11:39
But the machine doing the conversion **now** is set to **BST** now. @ammoQ – alk Jun 30 '14 at 12:55
If you don't want local time, don't use `localtime()`; use `gmtime()`! – Jonathan Leffler Jul 09 '14 at 00:48

localtime() is showing 0 microseconds since 1970 as one hour

0 Answers0