Simplify the following text for a Grade 10 native English-speaking person.
Original: The 2004 Summer Olympic Games , officially known as the Games of the XXVIII Olympiad , was a premier international multi-sport event held in Athens , Greece from August 13 to August 29 , 2004 with the motto Welcome Home .
Simplified: The 2004 Summer Olympics , officially known as the Games of the XXVIII Olympiad , were celebrated in Athens , Greece from August 13 , 2004 , until August 29 , 2004 .