Subject: Re: Apple IIe
Newsgroups: comp.sys.apple2
From: dempson@actrix.gen.nz (David Empson)
Date: Thu, 29 Apr 1999 02:21:12 +1200
Message-ID: <1dqzux7.yaqsf61rxc8lcN@dempson.actrix.gen.nz>
References: <7fqsb4$gqa$1@nclient5-gui.server.ntli.net> <19990425020551.11707.00001337@ng26.aol.com> <7fvuka$dff$1@news.rt66.com> <7g2ht8$2af$1@nnrp1.dejanews.com>
Organization: Empsoft
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<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