[Pnet-developers] timezone issues in pnet and ms.net

[Carl-Adam Brengesjo]

Cheers,

For those who don't know... I'm from Sweden; so right now the timezone 
here is CEST (+0200), normally it's CET (+0100). So if the time here is 
05:57 (24 hour format), the GMT/UTC time is 03:57.

But the timezone offset seems a bit off in pnet -- and in Microsoft's 
.NET. That's why I'm not sure this is a bug, or just *a deliberate 
incorrect behaviour to keep compat*.

I've made the following test:

test.cs:
using System;
class Test
{
 static void Main(String[] args)
 {
  String format = args.Length > 0 ? args[0] : "r";
  Console.WriteLine(DateTime.Now.ToString(format));
 }
};

On my linux box:
$ cscc -o test.exe -g test.cs -lSystem
$ ilrun test.exe
Thu, 07 Oct 2004 06:09:51 GMT
$ ilrun test.exe zzzz
+02:00
$ date
Thu Oct  7 06:09:57 CEST 2004
$ date -u
Thu Oct  7 04:10:00 UTC 2004

On windows (using cygwin):
$ ilrun test.exe
Thu, 07 Oct 2004 05:09:03 GMT
$ ilrun test.exe zzzz
+01:00
$ date
Thu Oct  7 06:09:08 WEDT 2004
$ date -u
Thu Oct  7 04:09:12 UTC 2004

On same windows box:
C:\> csc test.cs
Microsoft (R) Visual C# .NET Compiler version 7.10.6001.4
for Microsoft (R) .NET Framework version 1.1.4322
Copyright (C) Microsoft Corporation 2001-2002. All rights reserved.

C:\> test.exe
Thu, 07 Oct 2004 06:09:16 GMT
C:\> test.exe zzzz
+02:00
C:\> date /T && time /T
2004-10-07
06:09

Both machines are configured to CET with daylight saving -- CEST.

(note that the time differs somewhat due to the time it takes to type + 
change terminal etc and that they aren't synced)

What can clearly be determined by above test is:
1) pnet on cygwin belives GMT is +0100
2) pnet on linux belives GMT is +0200
3) .net belives GMT is +0200

If you didn't already know, GMT is +0000.

I have breifly looked into the problem and noticed that pnet formats r/R
(supposed to be RFC1123) with "ddd, dd MMM yyyy HH':'mm':'ss 'GMT'", 
meaning GMT is just appended to the current time in the current 
timezone, no matter what timezone you're in. I assume this is the 
behaviour of .NET aswell (from what I can tell from the SDK).

Either change the RFC1123 format string and have datetime parse a format 
which would either print the correct timezone name/offset (using offsets 
is recommended by RFC1123).
Or have all RFC1123 formatted strings be printed in UTC time... making 
the beahviour of just append "GMT" legimit.
I strongly recommend the former (or a simlar) solution :)

But I cannot explain why pnet on cygwin says the UTC offset is +0100 
when it should be +0200. However, my guess is that it's b/c Windows 
always treats the hardwareclock as localtime while linux defaults to UTC 
time, so pnet belives that the hardware clock is UTC time, while it 
really is just the daylight saving time.

As the date and time is specific to each computer, I'd like some 
comments on this by people with other timezone configurations before 
filing any bugs.

By the way, "zzzz" is *NOT* RFC1123 compilant. "zzzz" outputs timezone 
difference as "(+|-)HH:mm", while it should be "(+|-)HHmm". I know that 
this is the way Microsoft have done, but I just want you too keep this 
is mind when considering an alternative RFC1123 format string for pnet.
And as I said before, there's no format string for a RFC1123 formatted 
date :(
RFC1123 dates are same as RFC822, with the exception of using 4 digit 
year numbers instead of 2 digits (2004 vs 04) and some corrections.


/ ptha