The National Union of Journalists has announced that the 12-day South London strike has been moved to Thursday 18 June.
Originally set for Monday 15 June, the union said it was facing the possibility of a legal challenge from Newsquest that it said could "overshadow" the action.
The NUJ said that the company "raised a technical issue with the original strike notice", but added: "The union is confident that the company’s objections to the original notice were without basis."
The strike, over redundancies, staffing levels and pay, is now scheduled to take place until Wednesday 1 July.
The newspaper titles affected include: The Croydon Guardian, Sutton Guardian, Epsom Guardian, Wimbledon Guardian, Wandsworth Guardian, Balham and Tooting Guardian, Mitcham and Morden Guardian, Kingston Guardian, Surrey Comet, Elmbridge Comet, and the Richmond & Twickenham Times. The News Shopper series is also involved and has editions in Dartford, Lewisham, Greenwich, Gravesend, Bexley and Bromley.