Re: Apple IIe

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

<per_lindstrom@my-dejanews.com> wrote:

> I guess it depends on what kind of clock you use. I think the problem is that
> the first officially ProDOS supported clock (the ThunderClock???) did not
> actually tell you the year, only the date and the day of week (sic!). ProDOS
> then did a look-up in a table to find out the year.

[The ThunderClock is the correct answer.]

> If you have different clock hardware (for example a No-Slot-Clock or the real-
> time clock in the Apple IIGS) I don't think you need to update the calendar
> table.

Also correct.

> The internal storage of dates in ProDOS allows for years up to 2027 (1900 +
> 127).

The year field may be seven bits, but the rules for the usage of the
field mean that it is not allowed to contain a value higher than 99.

The rule states that year values 0-39 are 2000 to 2039, while 40-99 are
1940 to 1999.

This rule was introduced relatively recently (about 1992?), and is
covered in a technical note.  Older software which does date comparisons
or displays a four digit year are likely to have problems.

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