This is a very incomplete listing of some of the times that Trump has changed position on issues over the years. Please check back later.
For an idea how these position changes will hurt Trump in any general election see Steven Colbert's parody:
Trump has changed party affiliation several times. These are the dates on which he established or changed party affiliation:
July 1987: Republican
October 1999: Independent
August 2001: Democrat
September 2009: Republican
December 2011: No Party
April 2012: Republican
(1.) Joshua Gillin, "Bush says Trump was a Democrate longer than a Republican 'in the last decade,'" Politifact.com, August 24, 2015,http://www.politifact.com/florida/statements/2015/aug/24/jeb-bush/bush-says-trump-was-democrat-longer-republican-las/ (cites New York City Board of Elections records)
Trump has changed from being very pro-choice to being pro-life. These are some dates and positions:
1999, NBC's Meet the Press: very pro-choice.
2000, The America We Deserve: pro-choice but support a ban on partial birth abortion.
Feb. 2011, Conservative Political Action Committee, pro-life
January, 2015, Interview Mark Halperin of Bloomberg News: pro-life with exceptions for rape, incest, or protect life of the mother.
(1) Jon Greenberg, "Fiorina: Trump's abortion flip-flop," Politifact.com, August 11, 2015, http://www.politifact.com/truth-o-meter/statements/2015/aug/11/carly-fiorina/fiorina-trumps-abortion-flip-flop/