Re: No-Slot Clock

[dempson@actrix.gen.nz (David Empson)]

TEXAS II - AppleWorks <a2mg@aol.comNomail> wrote:

> >It clearly says Friday January 1, 1990
> 
> According to Glen Bredon, this is caused by a bug in ProDos.

Which part of ProDOS?  The kernel has no code to display the date, or
even any code to manipulate it.  ProDOS just uses the date/time provided
by the clock driver.

There could be a bug in the clock driver, but it would only affect one
specific type of clock (e.g. the Thunderclock or clones, in the case of
the built-in clock driver).

The clock driver should be setting the year field in the date to 0 for
2000.  It is up to applications which display the date to correctly
interpret this as 2000 instead of 1900.

Year values of 100 through 127 are illegal.

(See ProDOS-8 Technical Note #28 "ProDOS Dates--2000 and Beyond" for
full details.)

BASIC.SYSTEM doesn't display four digit years, so that leaves Apple's
System Utilities as the only remaining part of the system software which
might misreport the date.

There could be an issue with the Thunderclock driver's date table
running out of years, but there is a patch program included with the
current system disk which updates this.  (This must be done every five
or six years, since the table only holds seven years, up to two of which
may be leap years.  The table is used to calculate the year from the
month, day of month and day of week.)

This shouldn't affect a No Slot Clock, since the clock has a year
register and this is used directly by the No Slot Clock's driver.  (The
same applies with the IIgs clock.)

> I have tested it with a large number of programs and their so-called Y2K
> "problems," and he is absolutely right. Fixing ProDos to kick they year
> into 2000 (instead of 1900) is the solution in many (but not all) cases of
> Y2K wierdness.

Eh?  ProDOS doesn't store the century anywhere, so I don't understand
what is being fixed.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand