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UNiMUT aktuell: Der Tag der Abrechnung

Der Tag der Abrechnung (11.12.99)

Sollten unangenehme Persönlichkeiten dieser Tage im Bildungswesen und anderswo den Tag der Abrechnung nicht doch persönlich erleben, heisst dies dennoch nicht, dass ein Tag der Abrechnung (The day of reckoning) nicht sicher kommen wird. Wer sich in der theologisch-historischen Zeitrechnung, der Geschichte der Unices und der Programmmierung in C etwas auskennt wird sich eventuell nicht nur über den Y2k-Jahrtausendwechsel Gedanken gemacht haben, sondern auch schon über weitere wichtige(re) Datumsgrenzen. Dazu erhielt der UNiMUT rechtzeitig vor dem Jahresende per email einen wichtigen Text, den die UNiMUT-Redaktion Euch nicht vorenthalten will. Der Text ist zwar in Englisch, aber er ist dennoch auch für weniger geübte Menschen recht einfach lesbar. Freiwillige ÜbersetzerInnen melden sich bitte bei unimut@urz.uni-heidelberg.de.


This is the Y2K file that comes with UW imapd 4.7. It appears to be a bit more detailed than most would want but I think we should convert from the Gregorian to the Eastern Orthodox calendar ASAP (as soon as possible, d.S.) to avoid the Y20K issue.

QUESTION: Is c-client Y2K compliant?


There are no known Y2K issues in c-client; nor have there ever been any known Y2K issues in c-client from its inception.

You may wish to read the document calendar.txt for more information about the Y4K, Y20K, and Y45K issues. Assuming that c-client is still around in 2000-43,000 years, someone will have to deal with these.

Within the plausible lifetimes of people today, there are three known date-related issues in c-client which will have to be addressed in the future. If I am still alive when the first problem hits, I will be nearly 82 years old, and won't be maintaining c-client any more.


c-client, like most UNIX software, has Y2038 issues. On Tuesday, January 19, 2038 at 03:14:08 Coordinated Universal Time (also known as UTC, UT, or historically GMT), the clock on 32-bit UNIX systems will wrap around to a negative number; that is, from 0x7fffffff to 0x80000000.

c-client uses an unsigned long for its 32-bit time; however the C library on most UNIX systems uses a signed long and will interpret that time as being Friday, December 13, 1901 at 20:45:52 UTC.

Fixing this problem will require changing the C library to use either unsigned longs or a wider (e.g. 64-bit) value for time. Lots of work will need to be done on 32-bit UNIX systems as 2038 approaches. History suggests that most of the work will be done in the autumn of 2037... ;-) It's not known if anything is necessary to do to c-client other than just rebuild it with the new C library.

Going to 32-bit unsigned longs means that there will be a Y2106 bug that someone will have to fix. Hopefully nobody will even think of using 32-bit systems by then.


c-client assumes that 2-digit years with values of 70 or greater are in the 20th century, and that 2-digit years with values of 69 or less are in the 21st century. Time for UNIX began on January 1, 1970 and email on ARPAnet happened between the first TENEX systems shortly after that; consequently there is no ambiguity with email data with 2-digit years prior to the year 2070. This is used only when parsing a 2-digit year. c-client never generates one.

Fixing this problem requires convincing people not to use 2-digit years. This is a lesson that people should have figured out 70 years earlier with Y2K. Consequently, this may be a "non-problem." Otherwise, look in mail_parse_date() for the comment "two digit year" and change the statement as desired. [Note: do not change the definition of BASEYEAR since the UNIX port assumes that this matches when time began in the operating system.]


On January 1, 2098, the year in per-message internal dates will expire, since a 7-bit field is allocated for the year. c-client will mistakenly think that the day is January 1, 1970.

Fortunately, it is easy to fix this problem. Just increase the width of "year" in MESSAGECACHE in mail.h. If you make it 8 bits, it'll be good until January 1, 2216; 9 bits makes it good until 2482. 10 bits will push it back that you'd worry about the Y2800 question before having to increase it again. If you ignore Y2800, 11 bits will push it it back to having to worry about Y4K first.


At this year, you will need to decide whether to keep the Gregorian calendar, which is one day slow every 20,000 years, or go to the more accurate Eastern Orthodox calendar which is one day slow every 45,000 years. The Gregorian and Eastern Orthodox calendars diverge at this year.

There hasn't been any statement about how the international community will deal with the situation of the Orthodox calendar being one day ahead of the Gregorian calendar between 2800 and 2900. This will happen again between 3200 and 3300, and at gradually increasing intervals until 48,300 when the shift becomes permanent (assuming no Y20K or Y45K fixes).

If you wish to make the transition to the Eastern Orthodox calendar, rebuild c-client with -DUSEORTHODOXCALENDAR=1. You can then ignore Y4K and Y20K!


A little-known rule in the Gregorian calendar is that years that are evenly divisible by 4000 are not leap years. Unlike the other rules, this rule hasn't had effect yet, and won't for another 2000 years.

To fix the Y4K problem, just rebuild c-client with -DY4KBUGFIX=1.


Those of you who stuck with the Gregorian calendar have a problem; the calendar is now one day slow. The Pope has not made any statement about how this problem will be fixed. Maybe they'll declare that 20,004 is also not a leap year or something.

There is no fix for this problem in c-client.


Greeks, Serbs, Russians, and other Eastern Orthodox have spent the past 41,000 years laughing at westerners' increasingly futile efforts to keep the Gregorian calendar in order. The day of reckoning has come; the Orthodox calendar is now one day slow. The Patriarch of Istanbul (nee Constaninople) has not made any statement about how this will be fixed.

There is no fix for this problem in c-client.


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