A recent photo of a WWE production truck sporting the new WWE logo and promoting Smackdown lists “Thursdays 8/7c” as the air date rather than Friday.
Smackdown has been airing on Friday nights since Fall of 2005 when UPN decided to move it to what many in the television industry call the “death slot.” It has remained in that time slot ever since.
Originally the show made its debut on a Thursday on UPN and achieved more success while it aired on that particular day.
Smackdown moved to its current home, SyFy, in October 2010. There has been no official announcement yet regarding the move.
You can see the photo below. (Face blurred for privacy reasons)