CALVIN KLEIN DOUBLE-TIME: Come New York Fashion Week, Calvin Klein Inc. plans to rev up the party circuit right out of the gate with a Sept. 4 bash celebrating the 25th anniversary of its underwear and the launch of Calvin Klein Steel. Djimon Hounsou and Hilary Swank will do the honors as co-hosts. Hounsou models the brand’s underwear in the current campaign and Swank appeared in one in 2004. They won’t be the only ship-shape bods in the custom-designed space at Klein’s corporate headquarters, though: some former Calvin Klein Underwear models are also expected to turn up. Select revelers will have a week to recuperate before toasting Francisco Costa after two showings of the Calvin Klein Collection Sept. 11. Kate Bosworth and Julianne Moore will welcome guests to the private dinner in Costa’s honor at Ian Schrager’s much-anticipated Wakiya restaurant at the Gramercy Park Hotel.