Year 2000 issues in FTN software

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FTSC                             FIDONET TECHNICAL STANDARDS COMMITTEE
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Publication:  FRL-1011
Revision:     1
Title:        Year 2000 issues in FTN software
Author:       Michael Hohner, 2:2490/2520.17
Issue Date:   27 August 2003
Review Date:  N/A
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Contents:
                1. Introduction
                2. Generating Fidonet timestamps
                3. Interpreting Fidonet timestamps
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Status of this document
-----------------------

  This document is a Fidonet Reference Library document (FRL).
  
  This document arises from, and obsoletes FSP-1009.001 which was not
  promoted to a Fidonet standard.  The reasons for this decision are
  given below.

  This document is released to the public domain, and may be used,
  copied or modified for any purpose whatsoever.


Adjudication
------------

  The FTSC decided not to recommend FSP-1009.001 for promotion to a
  FidoNet Standard for the following reasons:

  * Obsolete.  The document was written 1997 to raise awareness of the
  problems and prepare Fidonet for the Year 2000 changeover.  We are
  now most definitely past it.

  * Describes no format or protocol, only an implementation detail
  for date handling.


Abstract
--------

  The year 2000 causes problems in many computer programs which use
  two-digit year numbers. Current Fidonet software faces the very same
  problems. This FSP specifies procedures which enable FTN software to
  run without problems after the year 2000.


1. Introduction
---------------

  Software using two-digit year numbers may cause problems in the year
  2000. When the year number rolls over from "99" to "00", some
  software may interpret the resulting year number as "1900" instead
  of "2000". Such programs may contain code like this:

     calendar_year = year_number + 1900;  /* wrong! */

  Fidonet software faces the very same problem: the year number in
  packed messages (see FTS-0001) has only two digits. Some programs
  interpreting this number incorrectly may decide that messages from
  the year 1900 are too old and discard them. Other programs probably
  just display a wrong calendar year.

  The long-term solution would be a transition to four-digit year
  numbers. However, this would require new data formats and cause
  every existing software to fail. So a short-term solution is
  required, resulting in only minimal changes in software. This FSP
  contains guidelines for proper year-number interpretation. The
  author encourages all FTN software authors to check their software
  for possible year-2000 problems (and release fixed versions during
  the next three years).


2. Generating Fidonet timestamps
--------------------------------

  This should not cause much headache. However, some software may use
  the following algorithm:

     year_number = calendar_year - 1900  /* wrong! */

  This will result in a three-digit year number in 2000 and lead to
  incorrect Fidonet timestamps.

  One correct algorithm is:

     year_number = calendar_year mod 100  /* correct! */


3. Interpreting Fidonet timestamps
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  We can make use of the fact that Fidonet didn't exist before 1980,
  i.e. no messages were created before 1980. So any year number
  smaller than 80 can't mean "year 19xx", but can only mean "year
  20xx". One algorithm for correct year number interpretation is:

     if year_number < 80 then
        calendar_year = 2000 + year_number
     else
        calendar_year = 1900 + year_number

  Fidonet software should only use the calendar year for further
  processing, not the year number from the timestamp.

  This solution will work until 2080, giving us another 80+ years to
  finally let some innovation happen in Fidonet.


A. Contacting the author
------------------------

  The author may be contacted electronically at the following
  addresses:

  Fidonet:    2:2490/2520.17
  Internet:   miho@osn.de

  Suggestions, comments and corrections are always welcome.


B. History
----------

  Rev.1, 19971229: Submitted as FSP.
  ------ 20030725: FSP-1009.001 reassigned to FRL-1011.001

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