On October 16, 2008, Williams took over as CEO, while Dorsey became chairman of the board. During his time as chairman, Dorsey joined several State Department delegations, including a trip to Iraq in April 2009, led by Jared Cohen. In November, when Iranians took to the streets in the Green Revolution, Twitter was scheduled to conduct maintenance of its site, which would entail temporarily shutting down Twitter's servers. Dorsey responded to a request from Cohen to delay the maintenance so that it would not affect the revolution in Iran, because Iranians were using Twitter to communicate and coordinate. Since President Obama had announced that there would be no meddling in Iran, the move sparked controversy. In February 2010, Dorsey was part of another State Department delegation, this time to Russia. On March 28, 2011, he returned to Twitter as executive chairman after Dick Costolo replaced Williams as CEO. On June 10, 2015, Costolo announced his resignation as CEO, effective July 1, 2015. Dorsey assumed the post of interim CEO upon Costolo's departure. He was named permanent CEO on October 5, 2015. On the day after the controversy about Twitter's new algorithms for tweets, Dorsey said it was a hoax.