Hi all,
Claudio Massao Kawata <[EMAIL PROTECTED]> wrote:
(..)
> Alwin Henseler ([EMAIL PROTECTED]) wrote
> about the way the leap years are calculated (once each four
> years, except once each century, except once each four
> centuries). I already knew that (many years ago, I needed a
> reliable calendar program for an "time-travel" adventure). He
> called it a "ridiculous system". I don't think it is ridiculous.
I meant the way you have to calculate it, this system itself
is genius indeed. To keep in sync with the sun & planets, 1 year
would have to be something like 365,24 days (don't know the exact
value, and this is not really a constant either, but shifting slowly
as well).
So, add a day every 4 years, and average year becomes 365,25
Hmm, to much...take out this extra day once every 100 years.
Hmm, a bit to little...add it back in every 400 years (you calculate
the aproximate value, which, you're right, is still not exactly on
the dot, but close).
Genius indeed, considering this was figured out back in the year 15xx
(I doubt it was that pope himself who did it, though).
> Why I mention all this?
> Because MSX don't have a 2000-year-bug, but a 2080-year-bug.
Wrong...
Whether or not a system is affected by a year 2000-bug, or similar
bugs (other systems use different ways of counting time, and suffer
similar bugs, but on different times), is a combination of factors:
-Hardware: MSX2 & up uses Ricoh RP5C01 compatible clockchip, which
DOES count wrong every 100th year (even Ricoh itself says so),
because it simply takes EVERY 4th year as a leap year. In the year
2000 this just doesn't show.
-System software
-BIOS
-Basic
-DOS date functions
Just showing that the date rolls over correctly from dec. 31, 1999 to
jan. 1, 2000 says something, but not that much. Showing that you can
store a date beyond 2000, and retrieve it correctly, doesn't say
everything either. You can only say for sure that this is processed
correctly, if you analyse the exact functions & code involved,
looking at what range of numbers are processed, how these are
'clipped' etc.
Did you check all the BIOS/diskROM/DOS code involved? Neither did I.
So that's not an 'okay', but rather a 'don't know, looks okay'
-Application software:
There's gotta be thousands of MSX programs, and probably hundreds or
more dealing with dates in one way or another. I would simply say
here: SURELY plenty of programs that don't get it right, so bugs are
in here as well.
All this ofcourse only with respect to the year 2000, take a broader
view, and you'll surely find more of such problems (like the year
2079).
(departing from MSX here...)
And this is no little software-update problem either. Some institute
estimated that all this work to get year-2000-ready will/has taken so
much effort, that it will lower economic growth with at least a full
percent (that's globaly, or for most industrialised nations).
Not doing this work to check and fix systems, would probably have a
similar effect because of all the problems that would result, when
non-checked system do go wrong.
That makes the y2k-problem a problem with at least a similar
magnitude as the earthquake in Kobe, Japan (you know, economists were
up in arms about the economic effect when this happened).
I'm not scared the world will come to an end as some might believe,
but calling al this plain 'paranoia', is equally far from the truth.
> More trivia about dates: the years start from 1, not zero, as
> most people think.
It is true....
> There is no zero-eth year, an error many people make
Sure there were years before 1!... I think the year '0' would
commonly be referred to as 'the year 1 before Christ', so:
3 before Christ
2 before Christ
1 before Christ
the year 1
the year 2
.
.
the year 99 (1st century)
the year 100 (2nd century)
Sure, technically the 2nd century would start only in the year 101,
and the 21st century in 2001, but who cares? That's just a matter of
convention. If everyone feels a next century started when 19xx
changed to 20xx, then it did, didn't it?
Alwin Henseler ([EMAIL PROTECTED])
http://huizen.dds.nl/~alwinh/msx (MSX Tech Doc page)
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