If you saved your 2005 Enterprise wall calendar, you can use it for 2011! The only differences are variable holidays, like Ash Wednesday, Good Friday, Easter, Passover, and Hanukkah (I think that's all of them but not sure).
Unfortunately, if you have the 2006 calendar, you can only use it through February 28 for 2012, as 2012 is a leap year, but 2006 wasn't.
Unfortunately, if you have the 2006 calendar, you can only use it through February 28 for 2012, as 2012 is a leap year, but 2006 wasn't.