The World Series is over, but Major League Baseball and the MLB Players Union have jointly announced that they are delaying the start of the offseason. From the press release:
The Office of the Commissioner of Major League Baseball (MLB) and the Major League Baseball Players Association (MLBPA) today announced that in connection with the collective bargaining process they have agreed to delay the start of the free agency period for 24 hours, to 12:01 a.m. (EST), Sunday, October 30th.
The players association will release its list of free agents and potential free agents on Sunday, and those free agents will be able to sign contracts with new teams beginning at 12:01 a.m. on Thursday.
It’s already been clarified that the official start of free agency has no affect on CC Sabathia’s situation. His contract says he has until three days after the World Series to decide whether to opt out, so he’ll have to make that decision by Monday. 
Three other key dates to keep in mind…
Last date for teams to offer salary arbitration to ranked free agents. The deadline is at midnight.
Last date for a player who declared free agency to accept an arbitration offer from his former team. The deadline is midnight.
Last date to tender contracts. Again, the deadline is midnight.