Key dates of Brexit By facebooker_10219127497919693 Jan 23, 2013 Mention of brexit by Cameron May 7, 2015 Referendum promised Feb 22, 2016 Date of referendum announced Jun 23, 2016 Referendum Jun 24, 2016 Cameron resign Jul 12, 2016 Theresa May: Prime Minister Jan 17, 2017 May announce brexit plan