Post by Mark L PappinI didn't promote that idea (and indeed would dispute it also), but
merely tried to explain what I saw as Jerome's terminology having been
misunderstood by you.
What I saw was the use of "Y9K bug fix" as an imaginative way to say
"add support for dates way beyond the current upper limit", but others
such as you did not see this meaning. Since Jerome explicitly stated
that years beyond 9999 would not be supported by this new scheme, it
seemed obvious to me that there was no attempt to address the "Y10K
problem".
Jerome's later posts make it clear to me that he had not in fact
intended "Y9K bug fix" to be interpreted as the witticism I saw.
Jerome Fine replies:
I thought that more information concerning the problems associated with the
implementation of any Y9K compliant software might help to clarify the
situation.
I subscribe to a list which enjoys looking at attempts to make changes
to the
calendar. Many of the individuals are EXTREMELY capable astronomers
who are able to understand the extremely complex relationships which result
in the orbits of the planets around the sun along with the spin of the
Earth about
its axis.
The current Common Era (aka Gregorian) Calendar which was first used
in 1582 introduced a modified set of rules to stop the drift of the Julian
Calendar which had then been in use for about 1600 years. In 1582, the
accumulated drift was over 10 days, i.e. the Northward Equinox which
was supposed to occur on about March 21st each year was late by about
10 days each year due to the rules used by the Julian Calendar. The new
modifications to the rules were probably just about the minimum required
at the time and, as many of us are aware, dropped 3 leap days out of every
400 years, specifically the leap days for the century years which are not
evenly divisible by 400. So, in the recent past, the years 1700 CE, 1800 CE
and 1900 CE were not leap years, i.e. they did not include a February 29th.
On the other hand, 2000 CE did include a February 29th, as will 2400 CE,
2800 CE, etc. while 2100 CE, 2200 CE, 2300 CE, 2500 CE, etc. will not
include a February 29th.
The difficulty is that these rules for the Common Era Calendar result in
a year
with exactly 365.2425 days while the actual Northward Equinoctial year
has only
about 365.2423 days. Over the next 8000 years, this will again result
(if no new
modifications are implemented to the current Common Era Calendar) in a drift
of when the Northward Equinox occurs. However, because the drift is so
small,
it will be around 4000 CE that a change needs to be made to the rules -
and even
then, the drift will still be less than a day. Or at least, that is the
best current
estimate. A discussion of "Why March 21st?" can be found at:
http://www.sym454.org/mar21/
http://individual.utoronto.ca/kalendis/mar21.htm
Within this link, and much more interesting, are two graphs which
provide the
"Gregorian Calendar Date at the Astronomical March Equinox" or the dates of
the Common Era Calendar when the Northward Equinox occurs. The graphs
provide the dates from 1582 CE up to 2400 CE followed by the dates from
1500 CE up to 8500 CE:
http://individual.utoronto.ca/kalendis/equinox/Gregorian_ME.pdf
There is another page which provides other information which is also
very interesting.
The Length of the Seasons is at:
http://individual.utoronto.ca/kalendis/seasons.htm
Contained with in this page are links to the Graphical Analyses of the
Length of the
Solar Year which includes a number of graphs. For my purposes, the
three most
useful graphs are the Mean Equinoctial and Solstitial Year Lengths at:
(a) 10,000 BCE to 15,000 CE
http://individual.utoronto.ca/kalendis/solar/Mean_Solar_Years_15K_L.pdf
(b) 50,000 BCE to 50,000 CE
http://individual.utoronto.ca/kalendis/solar/Mean_Solar_Years_50K.pdf
(c) Uncertainties due to the Slowing Earth Rotation Rate
Mean Northward Equinoctial Year Length, with varying Delta T rates
http://individual.utoronto.ca/kalendis/solar/EqSolst_Years_vary_DeltaT.pdf
The last three graphs show that until about 30,000 CE, the estimated
length of the
year will likely be longer than 365.24 days. On the other hand, if
other unanticipated
factors reduce the Rotation Rate of the Earth MUCH more quickly, then it is
conceivable that the length of the year could fall below 365.24 days as
early as
10,000 CE. The reason that I have chosen 365.24 days is because the rule
changes required to prevent drift between the actual date of the Equinox and
a fixed date such as March 21st will be the complete elimination of leap
days
for ALL century years, including century years divisible by 400. Note that
even dropping the one century year divisible by 400 will probably not be
required
until at least 4000 CE (at least that is the most probable current best
estimate);
consequently, the rules for the current Common Era (aka Gregorian) Calendar
rules should not require any changes for a VERY long time.
However, by 10,000 CE, it is almost certain that some modification to the
rules will be required to reduce the drift - if that is considered to be
an important
aspect to the humans who live at that time and many other factors, which are
obviously impossible to predict at this point, remain the same.
If you have read all the way to the end and looked at the charts, do you now
understand why I chose Y9K as the next goal?
Comments would be appreciated, especially comments which provide for a
possible resolution of the problem. I have considered one solution which is
a table of the years in which the extra leap day of February 29th is dropped
since up until 10,000 CE, there should be very few. The table could be
updated as required when and IF it ever becomes an adopted fact. The
key point is that once the code to use the table is in place, changes to
the rules may be very arbitrary, but could still handled at least until
the length
of the year is less than 365 days - assuming that the basic current Common
Era Calendar is retained in its present form as basically was been done when
the rule changes were made to the Julian Calendar to produce the Gregorian
Calendar, i.e. (other than the changes made when implementation occurred
along with the days which were dropped when the Gregorian Calendar
first became active,) the rule changes for leap years specified that the
three
century leap years in the Julian Calendar which are not evenly divisible by
400 were no longer leap years in the Gregorian Calendar. For a future
modified
Common Era Calendar, the first rule change may be to eliminate leap years
which are evenly divisible by 4000. However, based on the graphs which have
the above links, a rule may not be possible. A table driven list of
leap years
which have been eliminated might, therefore, be the way that these future
problems can be handled right now insofar as the code is concerned for
applications which are unlikely to have individuals who are interested, let
alone are capable, of making any changes in the future - the future being
10,000 CE.
Sincerely yours,
Jerome Fine