Updated: 13 July 2016, and will continue to be updated as more information is made known.
United Kingdom Joins EEC
On its 3rd application, the UK is finally admitted into the the European Economic Community (EEC), the EU's predecessor. Charles de Gaulle, President of France at the time, had vetoed the UK's first two applications, feeling that the UK was "incompatible with Europe." 
United Kingdom EC Referendum of 1975
Also known as the "Common Market Referendum," the UK used it to monitor support for the their continued membership in the European Communities (EC). Voters had a majority of support for EEC membership, with 67% in favor. This was historic, however, as it was the first UK-wide referendum ever held.
Maastricht Treaty Creates EU
Signed on 7 February 1992 by the EC members, the Maastricht Treaty created the European Union and led to the establishment of the single euro currency.
Eurosceptic UKIP Formed
United Kingdom Independence Party (UKIP), a Eurosceptic political party, is founded. UKIP will later become a key instrument in the Brexit vote and outcome.
PM Promises Referendum
PM David Cameron pledges an in/out referendum if the Conservatives win the upcoming election.
EU Referendum Act Approved
European Union Referendum Act 2015 (c. 36) was introduced to the House of Commons on 28 May 2015, approved by the House of Lords on 14 December, and was given Royal Assent on 17 December. Made provision for holding referendum in the UK no later than 31 December 2017.
Referendum Date Set
Prime Minister David Cameron announces that referendum would be held for voting on 23 June 2016.
Brexit Referendum Voting
The Electorate votes on the question, ``Should the United Kingdom remain a member of the European Union or leave the European Union?``
Brexit vote tallied over the night of 23 June, and the results emerge that the ``Leave`` campaign has won, garnering 51.9% of the vote to the ``Remain`` camp's 48.1%.
Scottish Gov't Wants Out
The Scottish Government announces that a second referendum on their independence from the UK is likely. Scotland had a majority ``Remain`` vote, and the news angered and saddened many there. They may try to join EU as sovereign nation.
David Cameron Resigns
Prime Minister David Cameron announced that he will resign by the autumn of 2016.
Brexit Emboldens Others
Prominent Eurosceptic figures from other countries praise the UK for Brexit and encourage a similar result at home: Marine Le Pen of France, Czech Prime Minister Bohuslav Sobotka, and the Dutch populist, Geert Wilders, among others.
Theresa May is New PM
Theresa May starts her job as British Prime Minister, after her competitor, Andrea Leadsom, pulled out days earlier. May is the UK's second female in this top position, after Margaret Thatcher.
UK Must Declare Withdrawal
Though the vote's results have been announced, the UK still must invoke Article 50 of the Lisbon Treaty by formally declaring their intentions to the European Union. Heads of many EU countries urge the UK to act swiftly, but many in the UK urge not to rush. Now that PM May is in charge, she will be urged to commence the withdrawal as soon as possible by her EU counterparts.
UK Must Renegotiate Trade Deals
The United Kingdom's trade deals with other nations were combined with the deals of all members of the European Union. The UK will have to negotiate new deals with other countries for trade purposes, as well as in other areas.