Daylight Saving Time flag in BIOS 
Author Message
 Daylight Saving Time flag in BIOS

According to my documentation, Int 1Ah/AH=02 and 03 return and set not
only hours, minutes and seconds in CH, CL and DH, but also a daylight
saving timecode in DL (O for standard time, 1 for DST).

Does anyone remember any application or OS actually using this
feature?

--

'Bear couteous greetings to the accomplished musician outside our
gate, [...] and convince him - by means of a heavily-weighted club
if necessary - that the situation he has taken up is quite unworthy
of his incomparable efforts.'   -Bramah, 'Kai Lung's Golden Hours'



Thu, 11 Oct 2001 03:00:00 GMT  
 Daylight Saving Time flag in BIOS
Not an answer to your question or maybe it is.

Info from "The Undocumented PC" by Frank van Gilluwe ISBN 0-201-47950-8

The RTC uses the last Sunday in April as the point for switching to
daylight savings time.
Currently daylight savings time in the U.S.A. starts on the first Sunday
in April.
This makes the RTC's daylight savings option fairly useless.
--

Eric P. van Westendorp  Tel: +31(0252)210579
Reigerslaan 22  2215NN Voorhout  Netherlands

Quote:

> According to my documentation, Int 1Ah/AH=02 and 03 return and set not
> only hours, minutes and seconds in CH, CL and DH, but also a daylight
> saving timecode in DL (O for standard time, 1 for DST).

> Does anyone remember any application or OS actually using this
> feature?

> --

> 'Bear couteous greetings to the accomplished musician outside our
> gate, [...] and convince him - by means of a heavily-weighted club
> if necessary - that the situation he has taken up is quite unworthy
> of his incomparable efforts.'   -Bramah, 'Kai Lung's Golden Hours'



Thu, 11 Oct 2001 03:00:00 GMT  
 Daylight Saving Time flag in BIOS

Quote:

>Not an answer to your question or maybe it is.

>Info from "The Undocumented PC" by Frank van Gilluwe ISBN 0-201-47950-8

>The RTC uses the last Sunday in April as the point for switching to
>daylight savings time.
>Currently daylight savings time in the U.S.A. starts on the first Sunday
>in April.
>This makes the RTC's daylight savings option fairly useless.
>--

The standard BIOS does not set this bit (RTC register B bit 0). Different
RTCs use different days for daylight savings, since these dates have been
changed by Congress. The Intel PIIX4 RTC, for example, uses the FIRST Sunday
in April. Read the data sheet for your particular RTC (and be aware that
many PCs have an RTC in both the IO controller and the chipset, so you need
to know which one is being used by your BIOS).

By the way, I'm not familiar with any application, BIOS or OS that uses this
RTC feature.

Flint



Sat, 13 Oct 2001 03:00:00 GMT  
 Daylight Saving Time flag in BIOS
That's what I meant.
If you can't be sure, it's better not to use it at all.
--

Eric P. van Westendorp  Tel: +31(0252)210579
Reigerslaan 22  2215NN Voorhout  Netherlands

Quote:


> >Not an answer to your question or maybe it is.

> >Info from "The Undocumented PC" by Frank van Gilluwe ISBN 0-201-47950-8

> >The RTC uses the last Sunday in April as the point for switching to
> >daylight savings time.
> >Currently daylight savings time in the U.S.A. starts on the first Sunday
> >in April.
> >This makes the RTC's daylight savings option fairly useless.
> >--

> The standard BIOS does not set this bit (RTC register B bit 0). Different
> RTCs use different days for daylight savings, since these dates have been
> changed by Congress. The Intel PIIX4 RTC, for example, uses the FIRST Sunday
> in April. Read the data sheet for your particular RTC (and be aware that
> many PCs have an RTC in both the IO controller and the chipset, so you need
> to know which one is being used by your BIOS).

> By the way, I'm not familiar with any application, BIOS or OS that uses this
> RTC feature.

> Flint



Sat, 13 Oct 2001 03:00:00 GMT  
 Daylight Saving Time flag in BIOS

Quote:

>According to my documentation, Int 1Ah/AH=02 and 03 return and set not
>only hours, minutes and seconds in CH, CL and DH, but also a daylight
>saving timecode in DL (O for standard time, 1 for DST).

>Does anyone remember any application or OS actually using this
>feature?

Win95.

--
/GreenGhost
________________________
Kill the spammer to mail me
________________________
http://hem.passagen.se/guffa/en/



Thu, 18 Oct 2001 03:00:00 GMT  
 
 [ 5 post ] 

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