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Date Adjustment At Turn of Century

IP.com Disclosure Number: IPCOM000061153D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Freeman, HL: AUTHOR

Abstract

The date is a frequently used item in data processing. The date is typically stored in a format where the year is a two-digit number with the high order digits truncated since they have always been "19". When the year 2000 arrives, havoc is threatened.

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Date Adjustment At Turn of Century

The date is a frequently used item in data processing. The date is typically stored in a format where the year is a two-digit number with the high order digits truncated since they have always been "19". When the year 2000 arrives, havoc is threatened.

Normally, the date is compared internally using a YYMMDD or YYDDD format. When comparing dates of like format, the date which generates a "high" condition code setting is considered the most recent date. After 1999 that will not necessarily be true.

Every component which ever uses the date for purposes of deciding a "most recent" situation, must use a simple adjustment factor. That factor would be fixed at each IPL. would be a two-digit unsigned number...AA - YY where YY is the low order two digits of the current year and AA is an adjustment value with a default of 50. A negative result mus complemented. Using 50 makes 50 years in the past least recent and 49 years in the future most recent; assuming that all of the years fit within the 100 year span.

In 1984, the adjustment would be 50 - YY =-33, or 67 complemented. Comparing 1983 vs 1984 would be (83 + 67) vs (84 + 67) or 50 vs 51. 51 is high and, therefore, 1984 is most recent.

If the above were modified using 10 to compute adjustment factor, the comparison result would be the same with 10 - YY = -73 or 27, when complemented, being used for adjustment.

The example which best demonstrates the need for the adjustment is at the onset of the year 2000. Assume that the comp...