Question:  Krzysztof Zimnoch once defeated the current heavyweight boxing champion, who has held his title since what year?
Context: Krzysztof Zimnoch (born September 6, 1983) is a Polish professional heavyweight boxer affiliated to the Hetman Białystok Boxing Club.  He holds an amateur win over current WBC heavyweight champion Deontay Wilder. Joseph Francis Hagan (better known as Philadelphia Jack O'Brien) (January 17, 1878 – November 12, 1942) was the world light heavyweight boxing champion.  Nat Fleischer, founder and editor of "The Ring" Magazine, ranked O'Brien as the No. 2 All-Time Light Heavyweight, and famed boxing promoter Charley Rose ranked him as the No. 3 All-Time Light Heavyweight.  O'Brien was inducted into the Ring Magazine hall of fame in 1968, the World Boxing Hall of Fame in 1987, and the International Boxing Hall of Fame in 1994. The Bare Knuckle Boxing Hall of Fame is a museum and hall of fame in Belfast, New York, dedicated to the sport of bare-knuckle boxing.  It is housed in barns that were once owned by the Greco-Roman wrestling champion and physical culture pioneer William Muldoon.  The heavyweight boxing champion John L. Sullivan, who fought in both bare-knuckled and gloved boxing contests, trained in these barns under Muldoon's guidance for his championship bout against Jake Kilrain in 1889.  The barns were originally across Main Street from their current location, on the grounds of the Belfast United Methodist Church.  They were bought, moved, and restored by Scott Burt when the church became no longer interested in maintaining them.  Burt opened the Hall of Fame in 2009, when it had its first induction class. NZNZWPW Heavyweight Championship is the top professional wrestling championship title in the New Zealand promotion New Zealand Wide Pro Wrestling (NZWPW).  It was the original super heavyweight title of Wellington Pro Wrestling and introduced as the WPW Super Heavyweight Championship on 3 December 2004.  The inaugural champion was Ruamoko, who defeated Les Barrett in a tournament final in Lower Hutt, New Zealand on 25 April 1992.  The title became vacant when Ruamoko suffered an injury in early-2005 and, after the promotion became New Zealand Wide Pro Wrestling, it was replaced by the current heavyweight championship first won by Island Boy Si on 25 March 2005.  The current champion Chad Howard in his first reign, is the longest reigning in history at + days. John Arthur "Jack" Johnson (March 31, 1878 – June 10, 1946), nicknamed the Galveston Giant, was an American boxer, who—at the height of the Jim Crow era—became the first African American world heavyweight boxing champion (1908–1915).  Johnson went on to become one of the most dominant champions of his time, and remains a significant historical figure in heavyweight boxing history, with his 1910 fight against James J. Jeffries being dubbed the "fight of the century."  Johnson was faced with much controversy when he was charged with violating the Mann Act in 1912, even though there was an obvious lack of evidence and the charge was largely racially based.  In a documentary about his life, Ken Burns notes that "for more than thirteen years, Jack Johnson was the most famous and the most notorious African-American on Earth". Percy Frank Goddard (27 November 1891- 8 December 1957) was a British boxer who became the heavyweight boxing champion in 1923.  Goddard's career begin in 1914 and it soon became apparent that he was one of the best boxers in the UK.  He became the British heavyweight boxing champion on 26 May 1919 having beaten Jack Curphey for the vacant British Boxing Board of Control (BBBofC) British heavyweight title.  Goddard lost the British heavyweight championship on 17 June 1919 to Joe Beckett. Deontay Leshun Wilder (born October 22, 1985) is an American professional boxer.  He has held the WBC heavyweight title since 2015, and in doing so became the first American world heavyweight champion in nine years, which was the longest period of time in boxing history without an American heavyweight champion.  As an amateur he won a bronze medal in the heavyweight division at the 2008 Olympics.  This led to his nickname of "The Bronze Bomber", which Wilder coined after Joe Louis, who was known by the nickname of "The Brown Bomber". Paul Berlenbach (February 18, 1901 – September 30, 1985) was the world light heavyweight boxing champion from May 30, 1925, when he wrested the crown from Mike McTigue, until July 16, 1926, when he was defeated by his nemesis Jack Delaney. " The Ring Magazine" founder Nat Fleischer rated him as the #10 best light heavyweight of all-time.  Berlenbach was inducted into the Ring Magazine Hall of Fame in 1971 and the International Boxing Hall of Fame in 2001. Tommy Burns (June 17, 1881May 10, 1955), born Noah Brusso, is the only Canadian-born World Heavyweight Boxing Champion.  The first to travel the globe in defending his title, Tommy made 11 title defences despite often being the underdog due to his size.  Burns famously challenged all comers as Heavyweight Champion, leading to a celebrated bout with the American Jack Johnson.  According to his biographer, Burns insisted, "I will defend my title against all comers, none barred.  By this I mean white, black, Mexican, Indian, or any other nationality.  I propose to be the champion of the world, not the white, or the Canadian, or the American.  If I am not the best man in the heavyweight division, I don't want the title." Lucas Browne (born 14 April 1979) is an Australian professional boxer and former mixed martial artist.  In boxing he has held the Australian and Commonwealth heavyweight titles, and made history in March 2016 by becoming Australia's first world heavyweight boxing champion after winning the WBA (Regular) title.  However, Browne was stripped of the title two months later for failing a drug test.  This ruling was then overturned in September, clearing him of any wrongdoing.  In November, Browne produced another positive drug test.
Answer: 2015