<Table> <Tr> <Th_colspan="2"> Boston Celtics </Th> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Td> </Td> <Td> 2017--18 Boston Celtics season </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Th> Conference </Th> <Td> Eastern </Td> </Tr> <Tr> <Th> Division </Th> <Td> Atlantic </Td> </Tr> <Tr> <Th> Founded </Th> <Td> 1946 </Td> </Tr> <Tr> <Th> History </Th> <Td> Boston Celtics 1946--present </Td> </Tr> <Tr> <Th> Arena </Th> <Td> TD Garden </Td> </Tr> <Tr> <Th> Location </Th> <Td> Boston, Massachusetts </Td> </Tr> <Tr> <Th> Team colors </Th> <Td> Green, black, gold </Td> </Tr> <Tr> <Th> President </Th> <Td> Rich Gotham </Td> </Tr> <Tr> <Th> General manager </Th> <Td> Danny Ainge </Td> </Tr> <Tr> <Th> Head coach </Th> <Td> Brad Stevens </Td> </Tr> <Tr> <Th> Ownership </Th> <Td> Boston Basketball Partners (Wyc Grousbeck, CEO and governor) </Td> </Tr> <Tr> <Th> Affiliation (s) </Th> <Td> Maine Red Claws </Td> </Tr> <Tr> <Th> Championships </Th> <Td> 17 (1957, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1968, 1969, 1974, 1976, 1981, 1984, 1986, 2008) </Td> </Tr> <Tr> <Th> Conference titles </Th> <Td> 21 (1957, 1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1968, 1969, 1974, 1976, 1981, 1984, 1985, 1986, 1987, 2008, 2010) </Td> </Tr> <Tr> <Th> Division titles </Th> <Td> 22 (1972, 1973, 1974, 1975, 1976, 1980, 1981, 1982, 1984, 1985, 1986, 1987, 1988, 1991, 1992, 2005, 2008, 2009, 2010, 2011, 2012, 2017) </Td> </Tr> <Tr> <Th> Retired numbers </Th> <Td> 21 (00, 1, 2, 3, 6, 10, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 31, 32, 33, 35, LOSCY) </Td> </Tr> <Tr> <Th> Website </Th> <Td> www.nba.com/celtics </Td> </Tr> <Tr> <Th_colspan="2"> Uniforms </Th> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Td> Home </Td> <Td> Away </Td> <Td> Third </Td> </Tr> </Table> </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Boston Celtics </Th> </Tr>

When was the last time the celtics won a championship