1
Mathematica 9/Mathematica 10, 115 bytes
Print["This program wasn't written in",a=" Mathematica ",If[b=Now==Now,9,10],", it was built for",a,If[b,10,9],"!"]
A bit late to the party... In Mathematica 9, Now remains unevaluated, and therefore equals itself. In Mma 10, each evaluation has a slight...