PRIME Minister Julia Gillard has surpassed Kevin Rudd's time in the Lodge to become Australia's 16th-longest-serving leader.

Today, Ms Gillard will have been prime minister for 936 days since seizing the top job from Mr Rudd in June 2010.

Labor's internal wranglings have been a constant niggle for the party, culminating in the ill-fated leadership challenge by Mr Rudd in February 2012, who was cajoled by Gillard supporters wanting to end speculation once and for all.

Next in Ms Gillard's sights on the list are Australia's first prime minister Edmund Barton (996 days), Labor prime minister Gough Whitlam (1071 days), and Liberal prime minister John Gorton (1155 days).

However, to make it to 12th place past Labor's John Curtin (1367 days), Ms Gillard will have to win the next election, due by November 30 this year - assuming there are no more leadership challenges along the way.

Australia's longest serving prime minister was Sir Robert Menzies, who served for a collective total of 18 years and 160 days (6735 days) over two terms.