It's big moment is now less than four days away. The first system failures will take place in New Zealand and Australia. There will be failures, but the bug's debut on the world stage will be far less dramatic than early publicity suggested.
The millennium bug is a straightforward computing problem. In fact, it is something of a misnomer: the bug is caused by the century ending, not the new millennium.
To save memory, old computer systems stored dates as two digits, so 1999 is just "99" in computerspeak. Computers think logically, so in a system with two-digit dates, 2000 becomes "00", which, numerically, comes before "99". The human brain is more sophisticated, so we can make the assumption that "00" means 2000, not 1900. Not so the computer.
Curing the bug on computers is largely a case of changing systems so as to use full, four-digit dates or, when that cannot be done, writing software that mimics the human mind and assumes that "99" is followed by "00", then "01".
The problem is the size of the systems at risk and the vast number of places where dates matter. Old, centralised computer systems with software written in the Seventies and early Eighties are the most problematic, as documentation is often out of date and the people who built the systems have often moved on or have retired.
Strangely though, the bug is, by and large, an IT success story. Barring an enormous oversight by almost the entire IT industry, the computer-driven world will not end on Millennium morning. The consensus among software experts is that we will see minor inconveniences in the next few months.
Civilisation as we know it will not grind to a halt.
Action 2000, the Government's official bug-watcher, is confident that all the UK's essential services have reached "blue" status, which means there will be no material disruption. "This covers everything from electricity, water and fuel down to the criminal justice system," says Tony Stock, director of operations at Action 2000.
"We are very pleased with the progress that has been made over the past two years." The Internet, too, should function properly. "The Net is an extremely resilient system," Mr Stock points out.
Action 2000's assessment of essential services includes the supermarkets, banks and telecommunications companies, so we should be able to buy food, withdraw cash and make phone calls in January with little or no disruption.
Chris Finch, UK country manager at the IT consultancy Merant-Microfocus, says: "I would be astonished if the lights go out. I do think systems will fail, but the failures will be invisible to the majority of the population. They will merely be minor inconveniences as the weeks go on."
Official figures show that larger businesses are on top of the problem. Disruption to FTSE-100 companies should be minor, so jobs and investments will be safe.
Companies are most at risk if they depend heavily on foreign markets and suppliers: Russia is one worry. UK businesses have contingency plans to cope. Over the past 18 months, economic commentators suggested that the millennium bug might trigger a global recession. That now seems unlikely.
If anything, economic activity should pick up in the new year as companies release the brakes on new developments which they had put on hold because of the bug. Several large financial-services companies, for example, plan to launch Internet- based products in 2000: the need to deploy staff on bug duties was one reason for not rolling out these this year.
Smaller firms face a trickier time. Modern PCs and software should be compliant, but older systems may not be. Software written for Windows 3.1 or DOS may well be vulnerable - upgrading is the easiest solution. Firms should pay attention to bespoke or customised software. The good news is that the problem can be fixed even after 1 January, although there is a risk of losing data.
Firms with networks should check that any servers and routers are Y2K- ready. Desktop PCs built after 1997 should be bug-free, and Macs are not affected. The retailer PC World says most of the computers it has sold since 1995 are compliant. Check for British Standard DISC PD2000-1 on the machine or in its paperwork.
"It is not too late to solve the problem," says Aled Miles, UK managing director of Symantec, a utility and anti-virus software publisher. "If you have an old PC you are at risk, so check the manufacturer's website. The issue of data is perhaps more serious, so take an hour or so to check it. It doesn't have to take a lot of time or cost a lot of money." Backing up crucial data on disk or paper is a sensible precaution.
The greatest threat now, some experts believe, is public over-reaction. There will be problems, but there is a technical solution for almost all of them, even if it means going back to paper records. "Our greatest concern has less to do with the bug than with human behaviour," Mr Stock says. "All the good work could be unravelled if people start to panic. There could still be short-term shortages - for example, pressure on the banking system."
Action 2000's advice is to stay calm. Go out and enjoy the festivities, but spare a thought and perhaps raise a glass for the thousands of IT specialists at their desks at midnight, just in case.
Government millennium office: www.millennium-centre.gov.uk
PC World millennium bug helpline: 0870 9012000