Five Issues for 1999-2001

The media has concentrated primarily on the big issue, the fact that many computer systems have only stored dates with two digit years.  While this is probably the biggest problem with the broadest reaching effects, there are four dates during 1999-2001 when computer programs may fail due to bad date-handling.  In this section, I'll briefly explain the problems and what systems may be effected.  The problems are listed in the order in which they will occur.

  • GPS Rollover
  • When September 9th = EndOfFile
  • Year 2000, the Biggie
  • Yes, 2000 is a Leap Year
  • And a Leap Year Has 366 Days
  • It Never Rains, But It Pours: Solar Storm Predictions
  • And For Extra Chaos, Bad Calls to the RTC New Stuff!
  • What Might Happen
  • GPS Rollover

    GPS stands for Global Positioning System, a set of satellites designed to help locate ships, airplanes, trucks, and anything else carrying a transponder.  Orbiting the Earth, they rely on an old method of pinpointing one's position (triangulation) with a new twist (from high altitude).  It's a very popular process.  In addition to the department of defense, an estimated ten million commercial planes, ships, and private individuals use the GPS system for navigation.

    On board each GPS satellite is a very accurate atomic clock.  GPS measures seconds, minutes, hours, days, and weeks since the system was started on 5 January 1980.  It tracks the number of weeks in a register that can hold a number from 0-1023.  Instead of going to 1024, it goes back to 0, like a car with 999,999 + 1 mile.  The GPS satellites will rollover on 22 August 1999.

    The GPS system is used to determine dates as well as location on millions of navigational units around the world.  It is also used as a method of recording time-of-day by many non-transportation systems, including many major banks in the U.S.   It is unknown whether or not these systems rely on GPS for date information as well.  It may very well be that many banking computers will not know the difference between 22 August 1999 and 5 January 1980.  Perhaps you will be charged for 19.5 years of unpaid interest.  Perhaps you bank will have to reset its computers.   Perhaps your bank will have to close for the day.  Not a pleasant thought if you planned to buy groceries with your ATM card. 

    And, let us not forget the possibility that major transportation systems like commercial aviation, shipping, and trucking may be shut down or delayed by problems in the GPS.  For more information, see What Might Happen.


    All About GPS - An in-depth site with step by step explanations of the GPS system, from Trimble Navigation Limited, a company which specializes in GPS equipment

    GPS Joint Service System Management Office (link no longer valid) - The military department that supports GPS user equipment for all services.

    Millennium (Y2K) and GPS End of Week (EOW) Rollover (link no longer valid) - A presentation by Capt. Jason Christ, GPS Y2K Lead Engineer, Navstar Global Positioning System, Joint Program Office

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    When September 9th = EndOfFile

    On 9 September 1999, the shorthand representation of the date will be 9/9/99.  The problem is that '9999' is a code in many COBOL programs which means "End of File."   

    Non-compliant applications can store dates in many different formats: MMDDYY and YYMMDD are probably the most popular (9 September 1999 stores as 090999 or 990909).  It is possible, however, that some systems are designed to handle date inputs of 9/9/99 and convert it to either of those two forms.  In this case, it is possible that 9/9/99 might be interpreted as an instruction to end the program running.  A minor possibility, but one that must be anticipated and planned for.


    New Stuff!

    99 Bug to Precede Y2K Bug - An article in the Washington Times about 9/9/99 (and 1/1/99)

    Y2K The Millennium Bug, part 4: "Other" Date Issues (link no longer valid) -  A comprehensive section of a fantastic site.

    Year 2000 Technical Resource Center (link no longer valid) - Developed for the U.S. Army's Year 2000 task force by the Technology Integration Center.

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    Year 2000, the Biggie

    Time is running out!

    In case you haven't heard, the cost of computers is dropping like a rock.  Just ten years ago $250 would have bought you a 170 Mbyte hard drive.  These days it will buy you a 6 Gbyte hard drive.  Today, you can buy a computer with a 4 Gbyte hard drive and 32 Mbytes of RAM for about $1000.  In the mid-60's a computer with a 2 Mbyte hard drive and 32 Kbytes of RAM cost about a million dollars!   Naturally, anything that programmers could do to save a few characters in RAM and on the hard drive was gratefully appreciated.  It was expected that the programs developed in the mid-60's would most likely be replaced in the 70's.  No one expected that they would still be in use at the end of the 90's.

    Dates all through the computer industry are stored with only two digits representing the year.  When dates are stored with the full four-digit year, the programs are designed to communicate with their impaired brethren. 

    Consider the following true story.  A 103-year-old man joins an HMO.  He gives his birthdate, including a year that begins with 18__.  The HMO has a two-digit field to store year-of-birth information.  The HMO's computer decides that the man is three years old and assigns him to a pediatrician.

    The big problem surrounding the Year 2000 will involve time periods that cross the date line.  It is obvious that a child born 1/1/2000 will be three years old on 1/1/2003, but how will a computer interpret the age of a child born 1/1/1999?  A compliant computer will correctly interpret the child's age as four years old.  A non-compliant computer may interpret the child as being 96, or -96, or maybe even -32,764 or -65532.   (For an explanation, click here.)  Maybe the computer will shut down with an "invalid age" message.  What if the computer belongs to an HMO that processes ten thousand customer records per day, most of them for children older than four?

    An HMO's computer system is not really critical (unless you are having chest pains and trying to get permission to go to the emergency room), but what if the electric company decides that you haven't paid your bill on time (in 99 or maybe 32 thousand years).   All sorts of situations can arise.  These are discussed in What Might Happen.


    Peter de Jager's official Year 2000 site (link no longer valid) - The ultimate reference by the man who broke the story back in 1993, in an article appropriately titled Doomsday 2000.

    Edward Yourdon's Web Site - Edward Yourdon is the brilliant co-author (with his daughter Jennifer of Timebomb 2000, which I feel is the definitive book on possible outcomes of the Y2K crisis.  

    New Stuff!

    Early Year 2000 Glitches Provide Sneak Preview - CNN reports that early detection helps promote the cure.

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    Yes, 2000 is a Leap Year

    It seems strange, but many people are still confused over whether the year 2000 is a leap year or not.  We all know that when a year is divisible by four (as was 1996) it is a leap year.  But there is an exception.  When a year is divisible by one hundred (as was 1900) it is not a leap year.  But there is further exception.  When a year is divisible by four hundred (as is 2000), it is a leap year.   The best (and funniest) explanation of the reasoning behind this was supposedly written in the help desk of Digital Equipment Corporation in answer to a complaint that their VMS operating system treated the Year 2000 as a leap year, which the complainant incorrectly thought was in error.

    Systems which correctly interpret 01/01/2000 as part of 2000 and not 1900 may still think that 28 February 2000 is followed by 1 March 2000. 


    Year 2000 Issues: Leap Year Problems and Resolutions (link no longer valid) -

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    And a Leap Year Has 366 Days

    Some computer programs keep track of the Julian date, that is the number of days in the year.  5 January would be 005, and 20 July would be 201.  If made Year 2000 compliant but not leap year compliant, these systems would handle correctly handle 29 February 2000 as 2000060, but would be stuck when confronted with the fact that 2000365 is 30 December, not 31 December. 

    The Year 2000 problem will not be over until 1 January 2001.   Coincidentally or not, that is the true start of the next millennium.


    Leap-Year software bug gives "Million-dollar glitch" - A computer program that didn't understand that 1996 was a leap year underwent massive system shutdown on 31 December 1996 at two aluminum smelting plants in New Zealand and Tasmania.  By the time the bug was discovered and corrected, both plants were damaged to the tune of one million New Zealand dollars.

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    It Never Rains, But It Pours

    One of possible results of the Year 2000 crisis is a disruption in power, either because of problems in the computer systems that provide the power or in the computer systems that bill you for your power consumption.  As an extra irony, we may lose power even in Year 2000-compliant systems.

    During periods of high sunspot activity, the magnetic particles emanating from the Sun are increased.  The increased particle output affects our Earth's atmosphere.  The Aurora Borealis is brighter and more vivid.  The atmosphere expands.  (A higher than normal sunspot season is blamed for the early re-entry of Skylab.)  The average temperature drops.  And magnetic storms disrupt power transmission.  The risk of Solar storm interruption of power is increased in Northern cities.  Ironically, the regions that will be coldest and most likely to need power for heating are most likely to lose power during a solar storm.

    NOAA's Solar Cycle 23 Project predicts that there will be a sun spot maximum from January 1999 through January 2001.  In addition to the obvious problems this may cause in power transmission, sun spots interfere with satellite transmission, and may cause additional problems in communicating with the GPS satellites.  We'll be well into solar maximum when the GPS date rolls over.

    Although I am writing this in August of 1998, about six months before the normal beginning of the solar peak, I am informed by a friend who works for Southern California Edison that a memo advising them to be on the lookout for solar storm-related blackouts.  This solar maximum shows signs of being unusually strong.


    New Stuff!

    Solar Eruption Causes Geomagnetic Storm on Earth

    Solar Cycle 23 Project

    Cosmic Storms Coming: Violent Outbursts of Gas From the Surface of the Sun Could Lead to Big Trouble Here on Earth (link no longer valid) - An article from Time magazine, 9 September 1996

    Upon completion of the engineering tests, Skylab was positioned into a stable attitude and systems were shut down.  It was expected that Skylab would remain in orbit eight to ten years.  However, in the fall of 1977, it was determined that Skylab was no longer in a stable attitude as a result of greater than predicted solar activity.  On July 11, 1979, Skylab impacted the Earth surface.  The debris dispersion area stretched from the Southeastern Indian Ocean across a sparsely populated section of Western Australia.
            -- from NASA's Skylab Operations Summary

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    And For Extra Chaos, Bad Calls to the RTC

    Your computer keeps track of the date and time with a module called the Real Time Clock.  Microsoft says that Windows NT™ prohibits direct access to the Real Time Clock.  Instead, applications are supposed to ask Windows NT™ for the date or time. 

    Most Real Time Clocks are not Y2K compliant, but that shouldn't be a problem.  Windows NT™ understands that when Real Time Clock says '00' that it is 2000 instead of 1900.  The problem is that some programs, especially those that require precise date and time information, access the Real Time Clock directly.   These programs may not be compliant. 

    As if we didn't have enough problems.


    Scope of Y2K Crisis Widens: Clock Problem Found

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    Resources for Other Problems

    January 1, 2000 Isn't the Only Doomsdate (link no longer valid) - Covers the above, plus UNIX EndOfFile (8 September 1991), UNIX rollover (19 January 2038), and the Social Security and telephone providers running out of numbers. 

    What Might Happen

    Now that we've examined the causes of our woes, let's take a look at what might happen if these issues are not resolved.


    Lauren Eve Pomerantz
    August 1998
    last updated 15 August 2007