Re: [Mono-dev] DateTime.Now gives a wrong time
On 12.10.2011 22:05, k0l0b0k.v...@gmail.com wrote:
> Hello guys, thanks for your replies. I think, I've understand the situation.
> Some weeks ago, Ukraine and Belarus has timezone changes by law, and now we
> are FET timezone (GMT+3, without DST). As Robert pointed, I've look into
> TimeZone.* methods, and their native implementations, and found, that wrong
> GMT offset brings by glibc's mktime function. But, it is not mktime bug
> (however, I'm not sure), it is mono issue - code from icall.c:5931:
>
> memset (&start, 0, sizeof (start));
>
> start.tm_mday = 1;
> start.tm_year = year-1900;
>
> t = mktime (&start);
>
> I've found, that setting only tm_year in start struct is insufficiently. At
> least tm_mon must be set too, to avoid this issue. Simple test:
>
> #include
> #include
> #include
>
> int main(int argc, char *argv[])
> {
> struct tm t;
> memset(&t, 0, sizeof(t));
> t.tm_year = 111; // 2011
> t.tm_mon = 10; // wrong tm_gmtoff will received if comment out this
> line
tm_mon = 0 means January 1st 2011. Back then, the offset was GMT+2,
Eastern Europe Time, so the call is correct.
The problem is not tm_mon = 0, because Mono does it on purpose
to get the first day of the year:
https://github.com/mono/mono/blob/master/mono/metadata/icall.c#L6013
Then it starts looping to find out when the GMT offset is changing:
https://github.com/mono/mono/blob/master/mono/metadata/icall.c#L6038
This probably happened at some date in March:
https://github.com/mono/mono/blob/master/mono/metadata/icall.c#L6063
Then it loops further to find out when the GMT offset changes again.
But this second change is never happening, because FET remains
forever at GTM+3 => Mono thinks it's still on DST for the rest of
the year.
I believe the fix is to remove the if-statement at
https://github.com/mono/mono/blob/master/mono/metadata/icall.c#L6076
because the code inside the if-statement must be executed
regardless of is_daylight's value.
Robert
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Re: [Mono-dev] DateTime.Now gives a wrong time
> On my Debian box (using debian packaged Mono) everything is fine.
>
> fog@ania:~$ csharp
> Mono C# Shell, type "help;" for help
> Enter statements below.
> csharp> Console.WriteLine("{0}", DateTime.Now);
> 12/10/2011 14:18:58
> csharp>
>
> fog@ania:~$ date
> Wed Oct 12 14:19:04 CEST 2011
>
> Can you show us your env?
>
> federico
>
> > user@server:~# date
> > Wed Oct 12 14:09:10 FET 2011
>
> FET? This is an interesting time zone:
> http://en.wikipedia.org/wiki/Further-eastern_European_Time
>
> It seems that Mono is thinking that you're now on EET
> (Eastern Europe Time, UTC+2), your former time zone.
>
> Either you don't have correct time zone files or there is
> a bug in Mono's GetTimeZoneData.
>
> Unlike other apps that only show the current time, Mono
> needs valid time probes for the whole year, so you can
> have invalid time zone info even if other apps seems to work.
>
> Maybe it helps when I tell you that on 2012/01/01 the bug will
> vanish on its own :)
>
> Robert
Hello guys, thanks for your replies. I think, I've understand the situation.
Some weeks ago, Ukraine and Belarus has timezone changes by law, and now we
are FET timezone (GMT+3, without DST). As Robert pointed, I've look into
TimeZone.* methods, and their native implementations, and found, that wrong
GMT offset brings by glibc's mktime function. But, it is not mktime bug
(however, I'm not sure), it is mono issue - code from icall.c:5931:
memset (&start, 0, sizeof (start));
start.tm_mday = 1;
start.tm_year = year-1900;
t = mktime (&start);
I've found, that setting only tm_year in start struct is insufficiently. At
least tm_mon must be set too, to avoid this issue. Simple test:
#include
#include
#include
int main(int argc, char *argv[])
{
struct tm t;
memset(&t, 0, sizeof(t));
t.tm_year = 111; // 2011
t.tm_mon = 10; // wrong tm_gmtoff will received if comment out this line
mktime (&t);
printf("2011: %d\n", t.tm_gmtoff);
return 0;
}
this is 100% reproducible inaccuracy for FET timezone, on all my accessible
machines:
* Debian Squeeze + mono 2.6.7 up to date
* Ubuntu 11.10 + mono 2.10.5 up to date
* Arch Linux + mono 2.10.5 up to date
on one machine, with Ubuntu 11.04, which is not updated last weeks, and stay
on EEST timezone - all works fine.
I'm vote for setting month value to "start" struct - today it happen with FET,
tomorrow it can be happen with any other timezone - world is changing all the
time...
Also, thanks God, I'm saving all times as UTC+0 in my server databases ;)
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Re: [Mono-dev] DateTime.Now gives a wrong time
On 12.10.2011 13:42, k0l0b0k.v...@gmail.com wrote: > user@server:~# date > Wed Oct 12 14:09:10 FET 2011 FET? This is an interesting time zone: http://en.wikipedia.org/wiki/Further-eastern_European_Time It seems that Mono is thinking that you're now on EET (Eastern Europe Time, UTC+2), your former time zone. Either you don't have correct time zone files or there is a bug in Mono's GetTimeZoneData. Unlike other apps that only show the current time, Mono needs valid time probes for the whole year, so you can have invalid time zone info even if other apps seems to work. Maybe it helps when I tell you that on 2012/01/01 the bug will vanish on its own :) Robert ___ Mono-devel-list mailing list Mono-devel-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-devel-list
Re: [Mono-dev] DateTime.Now gives a wrong time
On 12/10/11 13:42, k0l0b0k.v...@gmail.com wrote:
> Hello. I'm using Mono 2.6.7 (distro) on Debian squeezy, fully up to date, in
> my little enterprise environment.
> Some days ago, I've noticed a strangest behavior - all my services, based on
> mono shows a wrong time on calling DateTime.Now (with a difference of 1 hour
> ago). Any other services (php and RoR-based) gives normal current time.
On my Debian box (using debian packaged Mono) everything is fine.
fog@ania:~$ csharp
Mono C# Shell, type "help;" for help
Enter statements below.
csharp> Console.WriteLine("{0}", DateTime.Now);
12/10/2011 14:18:58
csharp>
fog@ania:~$ date
Wed Oct 12 14:19:04 CEST 2011
Can you show us your env?
federico
--
Federico Di Gregorio f...@initd.org
Ubuntu is an ancient African word meaning "I can't configure Debian".
-- somewhere on IRC
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