Question: The next New South Wales state election in which the Liberal/National Coalition government, currently led by Premier Gladys Berejiklian will be challenged by the Labor opposition, currently led by a member of the New South Wales Legislative Council since what date?

Context articles: Fred Nile
Peter Phelps (politician)
List of New South Wales state elections
Don Harwin
Melinda Pavey
Gladys Berejiklian
John Ajaka
Luke Foley
Victorian state election, 2018
New South Wales state election, 2019

Frederick John "Fred" Nile ED MLC (born 15 September 1934) is an Australian politician and ordained Christian minister.
 Nile has been a member of the New South Wales Legislative Council since 1981, except for a period in 2004 when he resigned to unsuccessfully contest the Australian Senate at the 2004 federal election.
 Nile was re-elected at the March 2007 state election and is currently Assistant President of the Legislative Council.
 He is the longest-serving member of the New South Wales parliament.
 In November 2009 he stated his decision to retire in 2015, but later announced his decision to accept the Christian Democratic Party (CDP) nomination for the NSW Legislative Council at the New South Wales State Election on 28 March 2015.
Peter Robert Phelps (born 7 May 1968) is an Australian politician.
 He has been a Liberal Party member of the New South Wales Legislative Council since March 2011.
 He contested the New South Wales Legislative Assembly seat of Drummoyne in the 1999 New South Wales State election.
This article provides a summary of results for elections to the New South Wales Legislative Assembly, the lower house in New South Wales's bicameral state legislative body, the Parliament of New South Wales, which came into being in 1856 when New South Wales achieved responsible government.
 New South Wales politics were initially non-partisan, with individual Members of Parliament choosing to align either with the Government or the Opposition.
 This changed at the 1887 election where, for the first time, candidates were members of official political parties.
 The first two major parties to form were the Free Trade Party and the Protectionist Party.
 The 1887 election saw the 79 members of the Free Trade Party elected form the government with the 37 elected Protectionist Party members form the opposition.
 The next election saw the Free Trade Party retain government but with a reduced majority.
 The 1891 saw the Australian Labor Party for the first time.
 These three parties then fought out the next two elections through to 1898.
 After Federation in 1901, the Free Trade Party changed their name to the Liberal Reform Party with the Protectionists becoming the Progressive Party.
Donald Thomas "Don" Harwin (born 5 July 1964 in Sydney), an Australian politician, is the New South Wales Minister for Resources, the Minister for Energy and Utilities, the Minister for the Arts, and the Vice-President of the Executive Council since January 2017 in the Berejiklian government.
 Harwin is a member of the New South Wales Legislative Council representing the Liberal Party of Australia since 27 March 1999; and served as the twentieth President of the New South Wales Legislative Council between May 2011 and January 2017.
 Harwin has been the Leader of the Government in the Legislative Council since January 2017.
Melinda Jane Pavey (née Shaw ; born 1969), an Australian politician, is the New South Wales Minister for Roads, Maritime and Freight since January 2017 in the Berejiklian government.
 Pavey has been a member of the New South Wales Legislative Assembly since 2015, representing the seat of Oxley for The Nationals.
 She was previously a member of the New South Wales Legislative Council between 2002 and 2015.
 A former party staffer, the Coffs Harbour businesswoman became the party's youngest New South Wales MP at the age of 33.
Gladys Berejiklian (Armenian: Գլեդիս Բերեջիկլյան , ] ; born 22 September 1970) is the 45th Premier of New South Wales and the Leader of the New South Wales Liberal Party, offices which she assumed on 23 January 2017 following the resignation of Mike Baird.
 She has been a member of the New South Wales Legislative Assembly since 2003, representing the seat of Willoughby.
John George Ajaka (born 13 January 1956), an Australian politician, is the President of the New South Wales Legislative Council.
 Until 23 January 2017, he was New South Wales Minister for Ageing from April 2014, the Minister for Disability Services from August 2013, and the Minister for Multiculturalism fom April 2015 in the second Baird government.
 Ajaka is a member of the New South Wales Legislative Council since 2007, representing the Liberal Party of Australia and he is the first Liberal Party Lebanese Australian member of an Australian parliament.
 Ajaka has previously served as the Minister for the Illawarra during 2013 and 2015 in the O'Farrell and first Baird government.
Luke Aquinas Foley (born 27 July 1970) is an Australian politician who serves as the Leader of the Opposition in the Parliament of New South Wales and as parliamentary leader of the New South Wales branch of the Australian Labor Party.
 Foley was a member of the New South Wales Legislative Council since 19 June 2010 until his resignation to contest the Legislative Assembly seat of Auburn at the 2015 New South Wales election.
The next Victorian state election is scheduled to be held on Saturday 24 November 2018 to elect the 58th Parliament of Victoria, including all 88 seats in the Legislative Assembly and all 40 in the Legislative Council.
 The four-year one-term incumbent Labor government, currently led by Premier Daniel Andrews, will attempt to win a second four-year term and will be challenged by the Liberal/National opposition, currently led by Opposition Leader Matthew Guy.
The next New South Wales state election is scheduled to be held on Saturday 23 March 2019 to elect the 58th Parliament of New South Wales, including all 93 seats in the New South Wales Legislative Assembly and 21 of the 42 seats in the New South Wales Legislative Council.
 The eight-year two-term incumbent Liberal/National Coalition government, currently led by Premier Gladys Berejiklian, will attempt to win a third four-year term and will be challenged by the Labor opposition, currently led by Opposition Leader Luke Foley.