CBS is moving Survivor from Thursdays to Wednesdays at 8 p.m. after eight years of being on Thursdays, ever since it was moved there for its second season.
In its press release, CBS says Survivor Nicaragua will be “a potent lead-off hitter” for the 9 p.m. series, Criminal Minds, and a new series, The Defenders. In that timeslot this fall, it will face ABC’s The Middle and a new sit com, Better Together; Fox’s drama Lie to Me; and NBC’s new drama Undercovers, which is produced by JJ Abrams.
More significantly, if CBS doesn’t change its mind for the spring, Survivor will face off against the newly shortened half-hour results show for American Idol 10.
Shuffling the 21st season seems to be CBS’ attempt to using its strength and its fans to hurt shows on other networks; CBS’ successful comedy The Big Bang Theory and new comedy Shit My Dad Says (based on the Twitter account) gets the Thursday at 8 timeslot, which means CBS will have a block of comedies to compete against NBC’s.
This actually returns Survivor to its original timeslot from its first season in the summer of 2000. After that, CBS made a bold move, moving it to Thursdays to face Friends. That eventually paid off, and the show consistently won its timeslot for years, with occasional exceptions.
http://www.realityblurred.com/realitytv/archives/survivor_nicaragua/2010_May_19_moved_to_wednesdays 
