Editing TIMELINE (section)

===May 2004===
* May 1 - The largest expansion to date of the European Union takes place, extending the Union by 10 member-states: Poland, Lithuania, Latvia, Estonia, the Czech Republic, Slovakia, Slovenia, Hungary, Malta and Cyprus.
* May 4 - A WNBC helicopter crashes in the Flatbush section of Brooklyn, New York. This event is covered by rival station WABC-TV.
* May 6 - The final episode of Friends airs on NBC, drawing an estimated 52 million viewers in North America.
* May 8 - Would-be "Saudi Princess" "Antoinette Millard" surfaces in New York City claiming that muggers had stolen jewels worth of $262,000 from her (she later proves to be an impostor).
* May 9 - Chechen president Akhmad Kadyrov is killed by a landmine placed under a VIP stage during a World War II memorial parade in Grozny.
* May 9 - Canada wins the World Ice Hockey Championship in Prague.
* May 10 - Philippine general election, 2004: Incumbent president Gloria Macapagal-Arroyo is re-elected.
* May 12 - An American civilian contractor in Iraq, Nick Berg, is shown being decapitated by a group allegedly linked to al-Qaida on a web-distributed video.
* May 13 - In India, the Congress Party wins a surprise victory in the elections to the Lok Sabha.
* May 14 - Frederik, Crown Prince of Denmark, marries Australian Mary Donaldson in Copenhagen.
* May 15 - Arsenal complete a whole English Premiership season unbeaten, 38 games.
* May 16 - A coup d'état in Chad against the President Idriss Déby fails.
* May 17 - Ezzedine Salim, holder of the rotating leadership of the Iraqi Governing Council, is killed in a bomb blast in Baghdad.
* May 17 - Massachusetts legalizes same-sex marriage in compliance with a ruling from the state's Supreme Judicial Court (Goodridge v. Department of Public Health).
* May 19 - Tony Blair is hit with a purple flour bomb in the chamber of the House of Commons during a session of Prime Minister's Questions.
* May 19 - Jeremy Sivits pleads guilty in a court-martial in connection with alleged abuse of Iraqi prisoners at Abu Ghraib prison in Baghdad.
* May 23 - A section of the ceiling in Terminal 2E at Paris's Charles de Gaulle International Airport collapses, claiming at least 6 lives.
* May 23 - Japanese prime minister Junichiro Koizumi visits North Korea, to secure the release of the families of the 9 abducted Japanese citizens returned earlier.
* May 26 - Terry Nichols is convicted by an Oklahoma state court on murder charges stemming from the 1995 Oklahoma City bombing.
* May 28 - G4techTV launches, a merger of G4 and TechTV (one of the most controversial network mergers in U.S. television history).
* May 29 - The National World War II Memorial is dedicated in Washington, DC.
* May 30 - Thousands of people in Hong Kong take to the streets to commemorate the 15th anniversary of the Tiananmen Square massacre.