Ubuntu affecting Windows XP clock

[Steve McIntyre]

On Fri, Sep 24, 2004 at 07:31:38PM +0800, John wrote:
>Steve McIntyre wrote:
>>
>>If you store local time in the RTC, there is no way for different OSes
>>to know if any DST changes have been applied. This leads to ridiculous
>>situations (like the first Win95 release) where an OS / several OSes
>>may each try to put the clock back/forward when they're booted after a
>>change.
>
>There's not?
>The tz environment variable that can be set on OS/2 as I recall (and 
>it's a long time since I used OS/2, longer ago since I had to cope with 
>DST locally) is that it has the transition dates.
>
>I would expect the difference from standard time might be applied to the 
>code that interprets the hardware clock.

If you're going to do that then you can just as easily offset from a
_real_ standard time.

>What actually happens I don't know, but it's wrong to say that the 
>hardware clock _has_ to be changed.

For the same reasons as below: MS-DOS compatibility. I've even heard
Microsoft people admit that putting local time in the RTC is stupid,
but they're apparently bound forever to do the wrong thing for
backwards compatibility.

In the past when I still had a toy OS installed dual-boot for playing
games, I just decided to give up on its time handling. It was easier.

>>The only sane way is to store UTC in the RTC and apply offsets when
>>you read/write to it. Then everybody's happy. The only reason Windows
>>still does the broken-by-design localtime thing is for backwards
>>compatibility with DOS, which didn't know any better.
>
>Indeed, early PCs didn't have a non-volatile clock. I think that came in 
>with the AT.

Yup.

-- 
Steve McIntyre, Cambridge, UK.                                steve at einval.com
"It's actually quite entertaining to watch ag129 prop his foot up on
 the desk so he can get a better aim."          [ seen in ucam.chat ]
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