National pledged to run a positive election campaign, and Labour said trust will be its central theme, at the start of an eight-week campaign leading to the 8 November election.
Labour leader Helen Clark announced the election date at a news conference at 12.35pm on Friday.
She said she had identified the election date some time ago, and is very optimistic of a successful outcome for Labour, which is hoping to be elected for a fourth term. She said the party will be releasing new policy shortly.
The Prime Minister said her Labour-led government had brought about a remarkable transformation for the better in New Zealand's economy and society.
Miss Clark told the media conference the National Party had attacked every major Labour policy aimed at making life better for families. She said National has flip-flopped on issues and only said what it thinks the country wants to hear.
Time for fresh perspective - Key
National says it will run a positive, forward campaign and will not resort to personality attacks.
Leader John Key says the election is about the future of New Zealand and New Zealand families.
Mr Key on Friday welcomed the election date announcement, saying new Zealanders have the chance to rule a line under the past three years.
However, he says Helen Clark is not in a position to talk about trust, after controversy about what she knows about the New Zealand First donations row.
Mr Key says he brings a fresh perspective to New Zealand, and is not a deeply ideological person who is embroiled in the debates of 30 years ago.
He says National will not look to run a campaign based on personalities, but on the issues facing New Zealand, and will not run what he calls a 'fear factor' campaign.
NZ First acted honourably - Clark
Miss Clark told Checkpoint she would not rule out working with New Zealand First after the election. The party's leader, Winston Peters, is embroiled in controversy over donations to his party and his legal fund.
She says New Zealand First has acted honourably as a party with a confidence and supply agreement, as has United Future.
The Labour leader said she has run a straight-forward and honest government, and stands by her integrity.
Parliament will be dissolved on 3 October, after a number of valedictory speeches from departing MPs. The last date an election could have been held was 15 November.
Radio New Zealand's political staff say in setting the election date the Government would have taken into account events such as a major rugby test on 1 November and the United States presidential elections 4 November.
They say the Government is also mindful of tax cuts taking effect on 1 October, and will want people to have had the benefit of those for some weeks before polling day.