Duke has won 5 NCAA Championships (tied with Indiana for fourth all-time behind North Carolina, UCLA and Kentucky) and appeared in 11 Championship Games (third all-time) and 16 Final Fours (fourth all-time behind North Carolina, UCLA, and Kentucky), and has an NCAA-best. 755 NCAA tournament winning percentage. Eleven Duke players have been named the National Player of the Year, and 71 players have been selected in the NBA Draft. Additionally, Duke has 36 players named All-Americans (chosen 60 times) and 14 Academic All-Americans. Duke has been the Atlantic Coast Conference Champions a record 20 times, and also lays claim to 19 ACC regular season titles. Prior to joining the ACC, Duke won the Southern Conference championships five times. Duke has also finished the season ranked No. 1 in the AP poll seven times and is tied with UCLA in total weeks ranked as the number one team in the nation by the AP with 121 weeks. Additionally, the Blue Devils have the second longest streak in the AP Top 25 in history with 200 consecutive appearances from 1996 to 2007, trailing only UCLA's 221 consecutive polls from 1966 -- 1980. As a result of such success, ESPN, in 2008, named Duke the most prestigious college basketball program since the 1985 -- 86 season, noting that "by any measure of success, Duke is king of the hill in college basketball in the 64-team era of the NCAA tournament." Since that designation, Duke has won two additional national titles in 2010 and 2015.

Based on this passage, when's the last time duke won a national championship? Let's give stream of consciousness first:
To answer this question, we should know that: Since that designation, Duke has won two additional national titles in 2010 and 2015.
So, the final answer is 2015.