Luis Filipe Madeira Caeiro Figo, OIH (Portuguese pronunciation: [lu'iS 'figu]; born 4 November 1972) is a retired Portuguese footballer. He played as a midfielder for Sporting CP, Barcelona, Real Madrid and Internazionale before retiring on 31 May 2009. He won 127 caps for the Portugal national team, a record at the time but later broken by Cristiano Ronaldo. Renowned for his creativity and ability to get past defenders as a winger, Figo is regarded as one of the greatest players of his generation.

Figo left Real Madrid to join Italian club Internazionale in the middle of 2005 on a free transfer after his contract with Madrid had expired. This meant that Figo would finally be able to play for a club in Italy, something he had the chance to do before his move to Barcelona, but was scuppered due to a dispute between the two clubs interested, Juventus and Parma. During the middle of 2008, Figo's compatriot Jose Mourinho joined Inter on a managerial level. This has been said to please Figo, as he would have several Portuguese teammates during the remainder of his stay at Inter.  On 16 May 2009, Figo announced his retirement from football, the same day Inter won the 2008-09 title, and re-confirmed this on 30 May; his final game was on 31 May against Atalanta at the San Siro. At Javier Zanetti's insistence, Figo captained the side for his very last match. He received a standing ovation from the crowd as he was substituted by Davide Santon. The free-kick he scored in extra time against Roma during the Supercoppa Italiana was his most memorable moment in Italy.  Figo said, "I am leaving football, not Inter." He was interviewed by Inter Channel after his last game against Atalanta and also said, "I hope to be able to help this club to become even greater also after my retirement. I will certainly work for Inter in the future in the club board. I never imagined that I was going to remain here for such a long time. What I will never forget is the love that I have received since my first day here from my teammates and president Massimo Moratti. I will never forget it; Inter have given me the chance to start a winning cycle with some extraordinary people." Figo was on the sidelines when Inter won the 2009-10 UEFA Champions League on 22 May 2010.

Answer the following question by taking a quote from the article: When did he retire?
On 16 May 2009, Figo announced his retirement from football, the same day Inter won the 2008-09 title,