Romania and Bulgaria joined the European Union.
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The Union Jack flag was flown for the first time in Dublin, Ireland, to commemorate the union between Great Britain and Ireland.
Same-sex marriage became legal in Austria.
Medical researcher Oswald Hope Robertson performed the first-ever blood transfusion using stored and refrigerated blood.
A monk put an end to gladiator fighting in Rome.
The country of Czechoslovakia peacefully dissolved into two nations, the Czech Republic and Slovakia.
