Cablevision Systems Corp. said that the planned spin-off of its cable networks will take place on June 30. The networks are AMC, the home of the “Mad Men” show, WE TV, IFC and The Sundance Channel. Cablevision shareholders will get one share of AMC Networks Inc. on June 30 for every four shares of Cablevision they hold on June 16. AMC Networks will start out with $2.43 billion in debt. AMC’s debt is being refinanced and part of the proceeds will be used to repay $1.25 billion of debt from Cablevision or its subsidiary CSC Holdings LLC. The AMC shares will trade on the Nasdaq stock market under the symbol “AMCX.”