The Eid al-Adha date is also in accordance with the Hajj authorities announcement of the Day of Arafah (the main day of Hajj) which is on Sunday, September 11.
It is mustahabb (highly recommended) for those who are not pilgrims to fast on the Day of Arafah. The Prophet (peace be upon him) was asked about fasting on the day of 'Arafah. He said: "It expiates the sins (minor) of the past year and the coming year." [Muslim]
10 Reasons Why We Should Take the First 10 Days of Dhul Hijjah Seriously