Barbados functions as a two-party system. The dominant political parties are the Democratic Labour Party (Barbados) and the incumbent Barbados Labour Party. Since Independence on 30 November 1966, the Democratic Labour Party (DLP) has governed from 1966 to 1976; 1986 to 1994; and from 2008 to 2018; and the Barbados Labour Party (BLP) has also governed from 1976 to 1986; 1994 to 2008; and from 2018 to present. The Democratic Labour Party government (DLP) held office with the then incomparable 1st Premier of Barbados became Prime Minister of Barbados, Errol Barrow from 4 December 1961 to 3 November 1966; 3 November 1966 to 9 September 1971; and from 9 September 1971 to 2 September 1976; and again from 28 May 1986 until his sudden death in office on 1 June 1987 for the then 4th Prime Minister of Barbados, Sir. Lloyd Sandiford with the Democratic Labour Party government (DLP) from 1 June 1987 to 20 January 1991; and from 20 January 1991 to 6 September 1994; the Barbados Labour Party government (BLP) held office with the then incomparable Prime Minister of Barbados, Tom Adams from 2 September 1976 to 18 June 1981; and from 18 June 1981 until his sudden death in office on 11 March 1985 for the then incomparable 3rd Prime Minister of Barbados, Sir. Harold St. John with the Barbados Labour Party government (BLP) from 11 March 1985 to 28 May 1986; the Barbados Labour Party government (BLP) held power from 6 September 1994 to 20 January 1999; 20 January 1999 to 21 May 2003; and from 21 May 2003 to 15 January 2008; the Democratic Labour Party government (DLP) held power with the then incomparable 6th Prime Minister of Barbados, David Thompson from 15 January 2008 until his death in office on 23 October 2010 for the then 7th Prime Minister of Barbados, Freundel Stuart with the Democratic Labour Party government (DLP) from 23 October 2010 to 21 February 2013; and from 21 February 2013 to 24 May 2018 for the general elections for the new Barbados Labour Party government (BLP). All of Barbadoss Prime Ministers, except Freundel Stuart, held under the Ministry of Finances portfolio. The Barbados Labour Party government (BLP) held power with the now 8th Prime Minister of Barbados, Mia Mottley from 24 May 2018 to present.

How many prime ministers belonging to the DLP were in office during the month of September?
2