Since its inception, the department has had its temporary headquarters in Washington, D.C.'s Nebraska Avenue Complex, a former naval facility. The 38-acre  site, across from American University, has 32 buildings comprising 566,000 square feet  of administrative space. In early 2007, the Department submitted a $4.1 billion plan to Congress to consolidate its 60-plus Washington-area offices into a single headquarters complex at the St. Elizabeths Hospital campus in Anacostia, Southeast Washington, D.C. The earliest DHS would begin moving to St. Elizabeths is 2012. The move is being championed by District of Columbia officials because of the positive economic impact it will have on historically depressed Anacostia. The move has been criticized by historic preservationists, who claim the revitalization plans will destroy dozens of historic buildings on the campus. Community activists have criticized the plans because the facility will remain walled off and have little interaction with the surrounding area.On January 8, 2009, the National Capital Planning Commission approved the Department of Homeland Security's plans to move into the campus of St. Elizabeths Hospital.In February 2015 the General Services Administration said that the site would open in 2021.
Question: How many years after the National Capital Planning Commission approved the Department of Homeland Security's plan to move into the campus of St. Elizabeth's Hospital did the General Services Administration say when the site would open?
Answer: 6