If they fail, the new year will begin with economic mayhem. If they succeed, they have set in motion one of the most ambitious economic projects this century, Europe's Economic and Monetary Union (EMU).

The final countdown to monetary union starts in Brussels on Thursday at 1030 GMT. The central banks of countries joining EMU will suggest the official euro conversion rates. Then the European Commission will confirm the figures, the EU's finance ministers will approve them and at approximately 1400 GMT - 1500 Central European Time - they will be published officially, in print and on the Internet at http://europa.eu.int/eurobirth.

Then the real work begins.

Three days

Across Europe central bankers, share brokers, investment fund managers, commercial bankers, currency dealers and bond traders will swing into action and convert billions of francs, guilders, Deutschmarks, schillings and assets in other currencies into euros.

On 4 January 1999 every trader needs to know the euro rules

They have just over three days to do the job. When the financial markets in Asia open again on Monday morning, 4 January 1999, everything has to be ready. Whoever deals with the eurozone - in shares, currencies or goods - needs to handle the euro, and banks and markets must be prepared to do so.

The tricky bit is that they all depend on each other. If a bank, a fund manager or a trader gets it wrong, their business partners and especially their customers and investors will suffer.

Roger Bates of Deutsche Bank describes it as "probably the biggest test to the financial community in current times". He predicts that "most banks and institutions - because of the amount of work that's got to be done and the short time they've got to do it - will be working 24 hour shifts."

Financial centres have geared up just for that. Some banks have booked hotel rooms for the legions of staff doing the conversion work over the New Year weekend. Catering has been organised and in the City of London, which normally is dead over the weekend, some restaurants and sandwich bars are opening specially to provide for the euro teams.

Getting ready

The financial sector has had a lot of time to get ready for this. Some banks began their preparations more than 18 months ago. Adjusting the computer systems was the greatest problem. All financial and accounting software had to be adapted to cope with the new currency, and special programmes had to be written to help with the change over.

The euro - "the biggest test to the financial community"

At very small finance houses simple calculators may have to do the job. Big companies like Mercury Asset Management, for example, will need more sophisticated instruments as they have to recalculate around $170bn worth of assets.

The UK is not in the first wave of countries joining monetary union, but London is the continent's financial centre and has to get ready too. More than half of Europe's investment funds are managed in the City and investments worth more than $600bn are at stake. For a Europe-wide picture add the conversion of hundreds of billions euros worth of currency transactions to the total government debt of the whole 11-country Euroland.

And there is more. Many banks in the eurozone plan to transfer their own business into euros and therefore have to recalculate their books and all historical data in their ledgers.

Rehearsing E-day

To cope with the task all parties involved have staged numerous rehearsals. Some companies have done three or more complete real-time trial runs to test whether their conversion teams can do the job in the short time available.

If the banks and brokers are to believed, all has gone well. They say that the new software is working. Nonetheless, experts predict that there will be hiccups on E-day when the euro is launched. Hundreds of different accounting systems used by numerous banks and financial markets will have to talk 'euros' to each other, and any misunderstanding will be like a stone thrown into a lake, sending ripples across the water.

Staff training is another problem. There has been plenty of it, but only the real-life experience will show whether all dealers properly understand the conversion rules. Anyway, brokers and analysts readily admit that it will take some time before they get used to the new euro prices. They know only one thing for certain: The euro will change their lives forever.