Re: [DotGNU]DateTime.Now is WRONG :)

[David Logan]

David Logan wrote:

> Hey guys, anyone know how come the DateTime class Now property returns 
> the wrong time?
>
> David Logan
>
> address@hidden temp]$ cscc -o tt.exe tt.cs
> address@hidden temp]$ ilrun tt.exe;date
> 6/30/04 10:37:46 PM -5
> Wed Jun 30 21:37:47 MDT 2004
> address@hidden temp]$ cat tt.cs
> class Test
> {
>   static void Main()
>   {
>                        System.Console.WriteLine(DateTime.Now);
>   }
> }
> address@hidden temp]$
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> Developers mailing list
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> http://dotgnu.org/mailman/listinfo/developers

Looking at the problem, it is in pnet/support/time.c in function 
ILGetTimeZoneAdjust. As shown below, it calls localtime(), and then 
modifies the returned timezone offset hours by one hour if the "isdst" 
variable is set. In my case, I my timezone is GMT-7. The returned 
timezone from the call is "GMT-6" and isdst=1. So this function modifies 
it by another hour and returns GMT-5.

The documentation for localtime and the tm struct is unclear. It seems 
that isdst=1 means that the returned timezone has already been modified 
for daylight savings. Is this correct? Should I inquire on the Unix 
newsgroup?

David Logan

ILInt32 ILGetTimeZoneAdjust(void)
{
#if !defined(__palmos__)
       static int initialized = 0;
       static int isdst = 0;
#ifdef HAVE_TM_GMTOFF
   static long timezone = 0;
#endif
       if(!initialized)
       {
               /* Call "localtime", which will set the global 
"timezone" for us */
               time_t temp = time(0);
               struct tm *tms = localtime(&temp);
               isdst = tms->tm_isdst;
#ifdef HAVE_TM_GMTOFF
               timezone = -(tms->tm_gmtoff);
#endif
               initialized = 1;
       }
       return (ILInt32)(timezone - (isdst ? 3600 : 0));
#else
       /* TODO */
       return 0;
#endif
}