<P> In 2013, Phil Mickelson won his first Open Championship at Muirfield . His victory meant that he had won 3 of the 4 majors in pursuit of the career grand slam, just needing the U.S. Open, where he has finished runner - up six times . </P> <P> In 2015, Zach Johnson denied Jordan Spieth his chance of winning the Grand Slam by winning an aggregate playoff over Louis Oosthuizen and Marc Leishman at the Old Course at St Andrews . </P> <P> The Open is a 72 - hole stroke play tournament contested over four days, Thursday through Sunday . Since 1979 it has been played in the week which includes the 3rd Friday in July . Currently, 156 players are in the field, mostly made up of the world's leading professionals, who are given exemptions, along with winners of the top amateur championships . Further places are given to players, amateurs and professionals, who are successful in a number of qualifying events . There is a cut after 36 holes after which only the leading 70 players (and ties) play in the final 36 holes on the weekend . In the event of a tie after 72 holes, a four - hole aggregate playoff is held; if two or more players are still tied, it continues as sudden - death until there is a winner . </P> <Ul> <Li> 1860: Contested over 36 holes, played on a single day </Li> <Li> 1892: Extended to 72 holes, played over two days </Li> <Li> 1898: Cut introduced after 36 holes . Those 20 or more strokes behind the leader were excluded </Li> <Li> 1904: Extended to a third day with 18 holes on each of the first two days . Cut rule unchanged </Li> <Li> 1905: Cut rule changed to exclude those 15 or more strokes behind the leader </Li> <Li> 1907: Qualifying introduced, replacing the 36 - hole cut and the contest reduced again to two days </Li> <Li> 1910: Cut reintroduced instead of qualifying, play being extended to three days again . Top 60 and ties made the cut . </Li> <Li> 1911: With an increase in the number of entries, the first two rounds were spread over three days, with 36 holes on the fourth day </Li> <Li> 1912: Qualifying reintroduced to replace the cut . Contest reduced again to two days </Li> <Li> 1926: Cut reintroduced . First Open with both qualifying and a cut . Extended again to a third day with 18 holes on the first two days . Those 15 or more strokes behind the leader were excluded from the final day . Days standardised as Wednesday to Friday </Li> <Li> 1929: Cut rule changed to ensure that at least 60 made the cut even if 15 or more strokes behind the leader </Li> <Li> 1930: Cut rule changed to top 60 and ties </Li> <Li> 1937: Cut rule changed to top 40 and ties </Li> <Li> 1938: Cut rule changed to be a maximum of 40 players . Ties for 40th place did not make the cut </Li> <Li> 1939: Cut rule changed to be a maximum of 44 players . Ties for 44th place did not make the cut </Li> <Li> 1946: Cut rule changed to be a maximum of 40 players . Ties for 40th place did not make the cut </Li> <Li> 1951: Cut rule changed to be a maximum of 50 players . Ties for 50th place did not make the cut </Li> <Li> 1957: Leaders after 36 holes go off last, replacing the random draw </Li> <Li> 1963: Cut rule changed to top 45 and ties </Li> <Li> 1964: Playoff reduced from 36 holes to 18, followed by sudden - death if still level </Li> <Li> 1966: Play extended to four days, 18 holes per day from Wednesday to Saturday . Cut rule changed to top 55 and ties </Li> <Li> 1968: Cut rule changed to top 70 and ties after 36 holes and then top 45 and ties after 54 holes </Li> <Li> 1970: Cut rule changed to top 80 and ties after 36 holes and then top 55 and ties after 54 holes </Li> <Li> 1971: Cut rule changed to top 80 and ties after 36 holes and then top 60 and ties after 54 holes </Li> <Li> 1973: Play in groups of three introduced for the first two rounds </Li> <Li> 1974: Use of "bigger ball" (1.68 in, 42.67 mm) made compulsory </Li> <Li> 1978: "10 - shot rule" introduced so that players within 10 shots of the leader make the cut even if outside the top 80 / 60 </Li> <Li> 1980: Play from Thursday to Sunday </Li> <Li> 1986: 54 - hole cut discontinued . Cut rule changed to top 70 and ties after 36 holes . Four - hole playoff introduced </Li> <Li> 1996: "10 - shot rule" dropped </Li> </Ul>

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