<human>: Daniel Milton Rooney (July 20, 1932 - April 13, 2017) was chairman of the Pittsburgh Steelers, an American football team in the National Football League (NFL), and son of the Steelers' founder, Art Rooney. Dan Rooney was elected to the Pro Football Hall of Fame in 2000 for his contributions to the game. He was credited with spearheading a requirement that NFL teams with head coach and general manager vacancies interview at least one minority candidate, which has become known as the "Rooney Rule". Rooney served as the United States Ambassador to Ireland, from July 2009 until his resignation in December 2012.

On March 17, 2009, President Obama announced he had nominated Rooney to become the next US ambassador to Ireland, citing the owner's longstanding support for Irish-American charitable causes. In 2008, Rooney gave $30,000 to a Democratic Party committee that aided Obama's campaign, according to CQ MoneyLine, a non-partisan group that tracks political contributions. According to David Lewis, a Vanderbilt University political scientist and the author of The Politics of Presidential Appointments, "giving coveted ambassadorships to political supporters is a relatively low-risk way for presidents to repay campaign debts."  Secretary of State Hillary Clinton swore him in as the new ambassador to Ireland on July 1, 2009. Ambassador Rooney presented his credentials to Irish President Mary McAleese on July 3, before making his first official speaking engagement at lunch hosted by the American Chamber of Commerce Ireland.  In an interview with The Irish Times in April 2011 Rooney mentioned that he would consider resigning his ambassadorship in order to campaign for Obama's re-election. However, in a prepared statement released after that interview was published Rooney stated, "I was asked what I could do to help [Obama] in the next election and I responded that the best thing I could do would be to help him campaign. Were I to do so, it would require my resignation as ambassador to Ireland. However, I am very pleased with my accomplishments to date and I intend to continue to carry out my duties." On December 14, 2012, he resigned as US Ambassador to Ireland and returned to Pittsburgh. He would eventually be replaced in June 2014 by Kevin O'Malley.  Rooney was the maternal great-uncle of actresses Kate Mara and her sister Rooney Mara. CANNOTANSWER

Using a quote from the above article, answer the following question: When was he ambassador to Ireland?
<bot>: On March 17, 2009, President Obama announced he had nominated Rooney to become the next US ambassador to Ireland,