What is the Year 2000 Problem?
This is a brief summary. For more information, consult any of the repositories
indexed under External reference information.
Warning. Before doing any testing,
make sure that disk files from your system are fully backed up, and that
you have a system startup disk which will start your computer in an emergency.
The providers of these pages cannot accept
any responsibility for any loss or damage to your system or data.
If in doubt, consult a qualified professional
NOTE: The four volumes Year 2000 - A Practical Guide for
Professionals and Business Managers, published by the British
Computer Society, are now available free
online in PDF format. The working party including Royal & Sun Alliance
Insurance, Bradford & Bingley Building Society and Shell International
Outline of the problem
Many present-day computer systems and programs are unable to handle dates
past the turn of the century. This is often called the Millennium Bomb.
The Pocket Website prefers to talk of the Century Challenge
because the same issue is faced whenever the century is needed to distinguish
between years. Nineteenth century (or earlier) dates cause the same problem
- for example, in
accession dates of old records in libraries
Birth dates of people who are now approaching their hundredth birthday
Architectural records of old buildings
Why did it happen?
Early computers were very limited in capacity. Memory for processing calculations
was very expensive. Magnetic tapes and magnetic disks were available for
off-line storage, but were also limited in capacity and were costly. To
do useful work with dates, the century was omitted to save space, time
It's a human problem too
We miss off the century for convenience even in everyday speech. We talk
about "the sixties" (the era of the Beatles), or "the nineties". Of course,
"the nineties" would have meant something very different to our grandparents
or great-grandparents, and that is the root of the problem.
Human beings don't need to be taught how to make assumptions from the
context about the missing century. Computers are not intelligent like that!
Leaving off the century gives what is commonly called a six digit
date. It may occur in various formats such as 12-Jun-95, 12/06/95 or
95/06/12. Symbolically we can represent these century-challenged formats
as dd-mon-yy, dd/mm/yy or yy/mm/dd.
Other formats are also possible. In the USA, mm/dd/yy is common
and 12/06/95 means 6th December 1995, not 12th June. This just makes things
Give me a simple fix! (sorry, no)
To fix this problem, you either have to give the program some means
to make an assumption about the missing century; or you have to
modify programs and data to make the century explicit. Including the century
means you move to an eight digit date such as 12/06/1995 (dd/mm/ccyy)
or 2002/06/12 (ccyy/mm/dd).
One good reason for changing is that, after the century change, six
digit dates such as 04/02/01 are highly ambiguous.
A common misconception is that systems will only fail after the clock
rolls over to 1 Jan 2000. This is not true! Systems may fail when they
first have to handle a date after 1 Jan 2000 ... for a program which
plans forward more than three years, this threshold has already been crossed,
in 1997. There is now only one complete tax year before the rollover: April
1998 to March 1999 in the US and the UK.
Can't I just sue somebody? (sorry, no again)
Of course, if you can prove your supplier was at fault then you might be
able to recover damages. Expect some major lawsuits, especially "class
actions" in the United States.
But even if you win, you'll still be left with the problem. Especially
if your supplier goes out of business as a result. And in any case the
legal definition of compliance is far from straightforward.
It seems far more useful to work positively with your suppliers if they
are cooperative. Most are. Keep legal action a long way in reserve; it's
a last resort!
... OK, so how much will it cost?
Well, as you'd expect, it depends! But the figures can be enormous and
are growing all the time. Worldwide, estimates range from 50 to 300 billion
(yes, billion) US dollars. Basically that's because a lot of the
work is labour intensive. Read on - it's not just about finding and fixing
code; there can be substantial testing and data conversion included too.
Now, in mid 1998, a lot of companies are waking up to find all the best
people and solutions providers have already been hired; they're having
to make do with less expert people, at higher cost. And those that already
have people are having to pay more to keep them. The early estimates of
around US$1.20 per line of Cobol code, or its equivalent, have probably
at least doubled.
Another way to look at it is that many enterprises are spending a third
or more of one year's IT budget to deal with the problem. That may be a
better guide as to whether your own estimates are reasonable.
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Where must we look
There are three main areas to look out for: hardware,
and data. Hardware problems include those which are
specific to embedded systems.
In addition, when you have fixed it, you have to make sure that you
don't reintroduce the problem. This is a particularly
easy trap to fall into if you exchange data with colleagues, customers
or others; their systems may not be compliant! You need to plan
your conversion in consultation with anyone you work with.
Consult your supplier and ask them for a statement about Year 2000 compliance
of your equipment and software. The British Standards Institution provides
Definition of Year 2000 Conformity Requirements.
For more information on conformance standards, see our Standards
Many vendors now provide information on their Web sites, and we provide
an index to some of this vendor information.
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Desktop, server and mainframe hardware
For PC users, the commonest failing of the PC itself is that, after 31
December 1999, it becomes unable to remember the date when it is switched
off. Most failing PCs seem to reset to 4 January 1980. This is quite easy
to test, and can be rectified through the DOS command DATE or through the
Windows system settings.
This makes it sound simpler than it is, however. On PCs you have to
take account of
Remember that many PCs, especially cheaper ones, use chips from sources
other than Intel (they are not necessarily better or worse, just different).
Also, some fixes work by providing a resident program which, in some circumstances,
may not actually kick in. You can still get incorrect dates back.
the built-in hardware/BIOS clock, and
the operating system time which is derived from it.
For more detailed information on the underlying problems, look in our
Apple Macintosh and the many Unix systems don't have this problem, though
Unix and older Macs will run out of dates later in the 21st century. Windows
NT is claimed to be compliant but must be run on compliant hardware. For
proprietary mainframe and server systems, consult the vendor.
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Embedded systems have microprocessors integrated into their control
or management systems. Sometimes these are general purpose processors similar
to those use in desktop computers; but they may be highly specialised devices.
Embedded systems can experience the date challenge in highly specific
ways. For example, failure of the system clock may cause the processor
to shut down even if the function which it is controlling doesn't appear
to be date dependent. Since equipment vendors often purchase chips from
several sources, machines which are apparently identical may have different
date challenge characteristics.
The Pocket Website has a page of information
about embedded systems.
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All your software needs checking.
Many software vendors will supply versions in due course which will
be capable of handling 21st-century dates. Most apply a technique called
to let the software make an intelligent guess if the century is omitted.
The problem with windowing is that different vendors make different
assumptions. In any case, the vendor's assumption may not suit your data.
It's your responsibility to match your needs to your software's
Expanding dates to 8 digits is safer if you can do it in time and get
it right! There are exceptions however, especially if:
If you have written your own software - and this includes desktop applications
like spreadsheets, if they store or manipulate dates - then you will need
to check it carefully. Business planning or forecasting systems may be
your highest risk - give them priority!
you are managing existing archived data
which you do not want to change, or
which you may not modify for legal reasons
you simply do not have time to check through archive data
which will only be used retrospectively and
which will never be modified from now forward
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Even if your computer hardware, its operating system and all your software
are fully Year 2000 compliant, you still need to manage the correctness
of your data. One of the oldest and still most valid principles of information
management is GIGO. Garbage In: Garbage Out.
When you have modified your software to handle year-2000 compliant dates,
it is more than likely you may need to convert existing century-challenged
data. Software conversion will not magically change data you've already
got from six digit dates to eight digit dates!
If software previously expected a six digit date (yymmdd ) but
now expects an eight digit date (ccyymmdd) you will need to modify
existing data accordingly. It's impossible to give general guidance, because
everybody's requirements will be different!
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Even when you have converted all your systems and data to the new standard,
the process is not complete.
You have to be on your guard if you receive data or programs from other
people or other organisations. If they have not converted, your friend's
spreadsheet may reintroduce the problem.
This is why some people call the Century Challenge a virus: it's not
malicious, but careless data exchange can "reinfect" your system.
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The key to success is planning. Work out exactly what you have to do, and
when you can do it. And good luck!
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Some key dates
Here are a few key dates to watch out for.
Based on information provided by Year 2000 discussion
group contributors, John Ivinson (BCS
Computer Bulletin, October 1997) and others.
01 Jan 1999 -- systems which only look one year ahead may show their first
06 Apr 1999 -- the start of the first tax year which goes past 1 Jan 2000
(in the UK at least).
09 Sep 1999 -- failures if "9999" has been entered in a date field to flag
end of file or some other condition.
24 Dec 1999 -- in many enterprises, the last working day before 1 Jan 2000.
31 Dec 1999 -- failures if "311299" (or "991231") has been used as a flag
01 Jan 2000 -- not a working day (a Saturday), but systems which run continuously
may fail. This could include many embedded chips. And people with hangovers.
04 Jan 2000 -- in most countries, the first working day; a Tuesday. Failed
systems may mismatch days of the week, and expect everyone to be at work
on the Monday!
29 Feb 2000 -- yes this date does exist, 2000
is a leap year. But not all systems will recognise it. If they
don't, the calendar will be a day out from this date forward.
01 Jan 2001 -- the first test of year-on-year comparions.
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Original material Copyright © Tony Law/Parkside Information Management