Date/Time setting

[Fritz Whittington]

On or about 2005-03-02 14:40, Fritz Whittington whipped out a trusty #2 pencil 
and scribbled:
> On or about 2005-03-02 06:14, Alan McDonald whipped out a trusty #2 
> pencil and scribbled:
> 
>> I synchronise some files across an ftp connection. The files comes from a
>> computer with the current date/time set, and my PC is also set with 
>> correct
>> time (both clock and hwclock return the correct time). But the files 
>> which
>> are writtin into the ftp directory are 13 hours ascew.. How can I correct
>> this? Where is the magic setting for making files writen to disk obey the
>> curret clock?
>> thanks
>> Alan
>>  
>>
> I'm presuming that this involves moving files from a Windows machine to 
> Linux, or vv.  Both Windows and Linux use UTC for timestamps.  The 
> difference is, in Windows you set the hardware clock to your local time, 
> tell it which timezone you're in, and it converts to UTC when stamping 
> file times.  Likewise, it converts timestamps back to local time for 
> DISPLAY purposes when you list the directory.
> Linux/Unix do it the other way.  The hardware clock is usually set to 
> UTC, you tell it what time zone you're in, and the DISPLAY of times will 
> be in local, but timestamps on files will be in UTC.
> 
> As a convenience to those who have one machine with a dual-boot of 
> Windows/Linux, most distros allow you to declare that the hardware clock 
> is actually not UTC, but local.  Then when Linux boots, it reads the 
> hardware clock, applies the TZ correction, then sets the system clock to 
> UTC.  If you tell Linux the hardware clock is UTC, then it doesn't apply 
> the correction on boot, just sets the system clock to the hardware 
> clock, and goes on as usual.
> 
> Windows of course, has no facility to be told that the hardware clock is 
> on UTC, and to correct for local time zone on booting.  So for Windows 
> you must set local time on the hardware clock.
> Another problem is that you can have your Windows time zone set 
> incorrectly, and someone has set the hardware clock to compensate.  So 
> if I in the US Central TZ set my Windows system to the Greenwich time 
> zone, then fiddle with the clock setting so that the time "looks 
> correct", then Windows will think it does not need to apply any 
> correction to get UTC, but all it's timestamps will then be off by 6 
> hours.  (A file created at 8:00 am local time would actually be stamped 
> as 0800 UTC, when it really should be stamped as 0200 UTC.)

Oooops!  That should be 1400 UTC, not 0200 UTC.  Sorry if the example caused 
even more confusion...

> Similar things of course can happen in Linux, in the opposite direction, 
> if you don't have your TZ data set correctly and just force the clock to 
> look like correct local time.
> 


-- 
Fritz Whittington
Man is by nature a political animal. (Aristotle, Politics)