DISC PD2000-1:1998 A Definition of Year 2000 Conformity Requirements

A DEFINITION OF YEAR 2000 CONFORMITY REQUIREMENTS

  
|  Preamble to the Summer 1998 amendment
|  BSI DISC originally published PD2000-1 in January 1997 and it has been 
|  widely adopted. A review of the document was conducted by the responsible
|  committee (BDD/1/3) in the spring of 1998 taking into account comments 
|  received. The committee considered that amendments to the fundamental 
|  conformity requirements were neither necessary nor desirable. The Definition 
|  and the four Rules are unchanged but, to add value to the document and 
|  aid its interpretation, the Amplification sections have been amended. 
|  This document, PD2000 1:1998, replaces the previous version of PD2000-1 
|  but does not change its requirements. An additional document PD2000-4, 
|  entitled “PD2000-1 in Action” will provide further information on 
|  PD2000-1:1998 together with information on its use.
|  Paragraph numbers have been enhanced in the Amplification section to aid 
|  referencing and substantial revisions to the document are indicated by 
|  side lines against the changed text.

   Introduction
   This document addresses what is commonly known as Year 2000 conformity 
   (also sometimes known as century or millennium compliance). It provides
   a definition of this expression and requirements that must be satisfied 
   in equipment and products which use dates and times.
|  It has been prepared by British Standards Institution committee BDD/1/3 
|  in response to demand from UK industry, commerce and the public sector. 
|  It is the result of work from the following bodies whose contributions 
|  are gratefully acknowledged: BT, Cap Gemini, CCTA, PricewaterhouseCoopers, 
|  Halberstam Elias, ICL, National Health Service, National Westminster Bank. 
|  Additionally, BSI DISC acknowledges the support of the Electronics and 
|  Information Industries Forum (EIIF), Action 2000, Taskforce 2000 and 
|  Digital Equipment as well as the original bodies for their participation 
   in the review of this document.
   BSI DISC would also like to thank the following organizations for their 
   support and encouragement in the development of this definition: 
   Barclays Bank, British Airways, Cambridgeshire County Council, 
   Computer Software Services Association, Department of Health, Ernst & Young, 
   Federation of Small Businesses, IBM, ICI, National Power, Paymaster Agency, 
   Prudential Assurance, Reuters, Tesco Stores.
   While every care has been taken in developing this document, the contributing
   organizations accept no liability for any loss or damage caused, arising 
   directly or indirectly, in connection with reliance on its contents except to
   the extent that such liability may not be excluded at law. Independent legal 
   advice should be sought by any person or organization intending to enter into 
   a contractual commitment relating to Year 2000 conformity requirements. 

|  This entire document or the Definition section (including the four Rules) 
|  may be freely copied (or downloaded to your PC) provided that the text 
|  is reproduced in full, the source acknowledged and the reference number 
|  of this document is quoted. It is recommended that the Amplification section
|  be included. References to “PD2000-1:1998” shall be interpreted as meaning 
|  the entire document.

   THE DEFINITION
   Year 2000 conformity shall mean that neither performance nor functionality
   is affected by dates prior to, during and after the year 2000.
   In particular:
   Rule 1	No value for current date will cause any interruption in
		operation.
   Rule 2	Date-based functionality must behave consistently for 
		dates prior to, during and after year 2000.
   Rule 3	In all interfaces and data storage, the century in any date 
		must be specified either explicitly or by unambiguous 
		algorithms or inferencing rules.
   Rule 4	Year 2000 must be recognized as a leap year.

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AMPLIFICATION OF THE DEFINITION AND RULES

1	 General Explanation
   1.1	 Problems can arise from some means of representing dates in computer
	 equipment and products and from date-logic embedded in purchased goods
	 or services, as the year 2000 approaches and during and after that year.  
	 As a result, equipment or products, including embedded control logic,
	 may fail completely, malfunction or cause data to be corrupted.
   1.2	 To avoid such problems, organizations must check, and modify if 
	 necessary, internally produced equipment and products and similarly
	 check externally supplied equipment and products with their suppliers.
	 The purpose of this document is to allow such checks to be made on a
	 basis of common understanding.
   1.3	 Where checks are made with external suppliers, care should be taken to
	 distinguish between claims of conformity and the ability to demonstrate
	 conformity.


|  2	 Amplification of the definition
|  2.1	 PD2000-1 (all editions) is solely concerned with the performance
|	 and functionality of a single version, release or system. It does
|	 not address differences in performance or functionality between
|	 different versions, releases or systems.
|  2.2	 Variations in performance immeasurably small in the context of use
|	 do not make a version, release or system non-conformant.

   3	 Amplification of the Rules
   3.1	 Rule 1
|  3.1.1 This rule is sometimes known as general integrity.
|  3.1.2 If this requirement is satisfied, roll-over between all significant
|	 time demarcations (e.g. days, months, years, centuries) will be 
|	 performed correctly.
|  3.1.3 Current date means today’s date as known to the equipment or product, 
|	 i.e. the actual date of operation.
|	 [NOTE - this refers to normal operation and does not prevent testing.]
   3.2   Rule 2
   3.2.1 This rule is sometimes known as date integrity.
   3.2.2 This rule means that all equipment and products must calculate, 
	 manipulate and represent dates correctly for the purposes for 
	 which they were intended.
   3.2.3 The meaning of functionality includes both processes and the results
	 of those processes.
   3.2.4 If desired, a reference point for date values and calculations may be
	 added by organizations; e.g. as defined by the Gregorian calendar.
|  3.2.5 No equipment or product shall use particular date values for special
|	 meanings; e.g. "99" to signify "no end value" or  "end of file" or "00"
|	 to mean "not applicable" or "beginning of file" unless the values in 
|	 question lie outside its possible date range.
   3.3   Rule 3
   3.3.1 This rule is sometimes known as explicit/implicit century.
   3.3.2 It covers two general approaches: 
	 (a) explicit representation of the year in dates: e.g. by using four
	 digits or by including a century indicator. In this case, a reference 
	 may be inserted (e.g. 4-digit years as allowed by ISO 8601:1988) and 
	 it may be necessary to allow for exceptions where domain-specific 
	 standards (e.g. standards relating to Electronic Data Interchange, 
	 Automatic Teller Machines or Bankers Automated Clearing Services) should
	 have precedence.
|	 (b) the use of inferencing rules: e.g. two-digit years with a value 
|	 greater than 50 imply 19xx, those with a value equal to or less than 
|	 50 imply 20xx. Rules for century inferencing as a whole must apply to
|	 all contexts in which the date is used, although different inferencing
|	 rules may apply to different date sets. Where any date element is 
|	 represented without a century, the correct century shall be unambiguous 
|	 for all manipulations involving that element.
|  3.4   Rule 4
|  3.4.1 A leap year is defined in ISO 8601:1988 (amended in 1991) as follows:
|        “year, leap:  In the Gregorian calendar, a year which has 366 days. 
|	 A leap year is a year whose number is divisible by four an integral
|	 number of times, except that if it is a centennial year it shall be 
|	 divisible by four hundred an integral number of times.”
|  3.4.2 Thus, for example, 2000 is a leap year but 1900 is not.
|
|  4	 General Notes
|  4.1	 For Rules 1 and 2 in particular, it is recommended that the allowable
|	 ranges for values of current date and dates to be manipulated be
|	 documented,recognizing that all systems have some limitation on
|	 the valid date ranges. The ranges may relate to one or more of the 
|	 feasible life spans of equipment or products or the span of dates 
|	 required to be represented by the organization's business processes.
   4.2 	 Tests for specifically critical dates may also be added (e.g. for leap 
	 years, end of year, etc.). Organizations may wish to append additional
	 material in support of local requirements.
   4.3	 Where the term “century” is used, clear distinction should be made 
	 between the “value" denoting the century (e.g. 20th) and its 
	 representation in dates (e.g. 19xx); similarly, 21st and 20xx.

ISBN 0 580 305 074

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