Many European central bankers are hearing the clock ticking as they prepare for full conversion to the euro in July 2002. After all, they are doing away with currencies that have endured wars, revolutions and plagues through the centuries. Concerns are high even in Eastern Europe. Indeed, for Peter Nicholl, the New Zealand-born governor of the Central Bank of Bosnia and Herzegovina, the problems are much shorter term and the ticking is likely to be a little louder.