May. 7, 2015: British voters elect a majority Conservative government. Cameron confirms in his victory speech that there will be an "in/out" referendum on European Union membership. Feb. 20, 2016: Cameron announces that he has negotiated a deal with EU leaders that gives Britain "special status." He confirms that he will campaign for Britain to remain in the 28-nation bloc. The referendum date is set for June.
Feb. 21: Cameron is struck with a severe blow when one of his closest Conservative allies, the media-savvy Boris Johnson, joins the “leave” campaign. June 16: One week before the referendum, Labour Party lawmaker and "remain" campaigner Jo Cox is killed by extremist Thomas Mair, who shouted "Britain First" before shooting and stabbing her.
June 23: Britain votes 52% to 48% to leave the European Union. June 24: Cameron says he will resign in light of the results because Britain needs "fresh leadership" to take the country in a new direction.
July 13: Following a Conservative Party leadership contest, Home Secretary Theresa May becomes prime minister. Oct. 2: May says Britain will begin the formal process of leaving the EU by the end of March 2017. To do this, the British government needs to invoke Article 50 of the EU's Lisbon Treaty.
March 29, 2017: The British government formally triggers Article 50, setting in motion a plan for Britain to leave the EU on March 29, 2019. June 8: A general election called by May to bolster her party's representation in Parliament to help with the Brexit negotiations backfires. Her Conservative Party loses its majority and continues in a weakened state as a minority government.
July 7, 2018: May and her Cabinet endorse the so-called "Chequers Plan" worked out at a fractious session at the prime minister's country retreat. The plan leads to the resignations of Brexit Secretary David Davis, Foreign Secretary Boris Johnson and others who favor a more complete break with EU.
Nov. 25: EU leaders approve a withdrawal deal reached with Britain after months of difficult negotiations. May urges the British Parliament to do the same. Dec. 10: May delays the planned Brexit vote in Parliament one day before it is set to be held because it faces certain defeat. She seeks further concessions from the EU.
Dec. 12: Conservative lawmakers who back a clean break from the EU trigger a no-confidence vote in May over her handling of Brexit. She wins by 200 votes to 117, making her safe from another such challenge for a year.
Jan. 15, 2019: The Brexit deal comes back to Parliament, where it is overwhelmingly defeated on a 432-202 vote. The House of Commons will end up rejecting May's agreement three times. April 11: Britain and the EU agree for a second time to extend the withdrawal deadline, originally scheduled for March 29, to keep Brexit from happening without a deal in place. The new deadline is Oct. 31.
June 7: May steps down as Conservative Party leader over the stalled Brexit agreement, clearing the way for Johnson to take over as Tory leader and Britain's prime minister. July 23: Johnson wins Conservative Party leadership contest.
July 24: Johnson takes office and almost immediately makes clear the U.K. with leave the EU on Oct. 31, with or without a deal. Aug. 28: Johnson says he will temporarily shut down Parliament by scheduling the Queen's Speech for Oct. 14. The speech normally is a formality that outlines the legislative agenda but since Parliament is ordinarily suspended beforehand, the move means the opposition will have less time to thwart a no-deal Brexit.
Sept. 3: Rebel Conservative Party lawmakers vote against the government in protest of Johnson's strategy. They are expelled from the party. Sept. 5: Johnson asserts he would rather be “dead in a ditch" than ask for another Brexit extension.
Sept. 9: A parliamentary measure that prevents the U.K. from leaving the EU without a deal becomes law. Sept. 24: U.K. Supreme Court rules government's suspension of Parliament was unlawful. Oct. 10: Johnson and Irish leader Leo Varadkar announce “pathway to a possible deal.''
Oct. 17: U.K. and EU announce they've struck a deal after U.K. makes concessions over Northern Ireland. Oct. 19: Parliament sits on a Saturday and demands to see legislation before approving the deal.
Oct. 22: Johnson puts Brexit legislation on pause. Oct. 28: EU gives UK “flextension'' until Jan. 31. Dec. 12: Johnson wins election decisively. Jan. 23, 2020: Withdrawal Bill becomes law. Jan. 29: European Parliament approves divorce deal.
Jan. 31: U.K. to officially leave the EU at 11 p.m.
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