Subject: Re: Timezones and stuff
To: NetBSD-current Users <>
From: Hellmuth Michaelis <>
List: current-users
Date: 03/29/1994 15:38:40
From the keyboard of Peter Galbavy:
> Watching the recent discussions on daylight saving time etc got me
> wondering again about the point of having the timezone hardwired
> into the kernel.
> I can't see why. Is there a major problem with assuming the RTC in
> a machine is set to the local (default) time ?

Yes, if you are able to use multiple OS'es and one of those is MSDOS, then
you have to manually adjust the RTC when a change happenes from non-DST
to DST and back to get the correct time in MSDOS.

One of my PC's has an AMI BIOS, which contains a DST option but which does
not work (=does nothing). I have heared (correct me if i'm wrong!) that
this switch enables the RTC DST switching:

both AMI and Phoenix document a DST bit in the RTC RAM (byte 0x0b, bit 0)
labelled "Enable DST", unfortunately it's not usable for our purposes
because the Motorola MC146818A Data sheet says about this bit: ".....On the
last Sunday in April the time increments from 1:59:59 AM to 3:00:00 AM. On
the last Sunday in October when the time reaches 1:59:59 AM it changes
to 1:00:00 AM. ..." - they hardcoded the position when the time change has
to occur.

So the time in a RTC on a PC on which xxxBSD is NOT the only operating
system is either the local time or the local time DST-adjusted by a MSDOS
user :-)

If NetBSD is the only bootable OS on machine it might be ok to have the
RTC run at GMT (or the modern equivalent of it), but for other situations
i see no straightforward solution ...

just my 0.02 ECU,
Hellmuth Michaelis    HCS Hanseatischer Computerservice GmbH    Hamburg, Europe
   Use of devices that are not officially supported can cause data loss, system
   panics and device damage.          (HP-UX 9.0, scsi(7): SCSI device drivers)