Via Starwars.com:
As the force grows stronger and Star Wars fans become more eager for the debut of the animated television movie Star Wars Rebels: Spark of Rebellion, Disney XD has moved up the debut by three days, to Friday, September 26 for verified users of WATCHDisneyXD.com and the WATCH Disney XD app for smartphones, tablets and connected TVs.
The new date will give verified WATCH Disney XD viewers a seven-day exclusive window to watch Star Wars Rebels before the global television debut Friday, October 3 (9:00 p.m., ET/PT in the U.S.) on Disney Channels around the world, ushering in the series beginning Monday, October 13 (9:00 p.m., ET/PT) on Disney XD.
Image from starwars.com