I'm no expert by any stretch of the imagination, but doing a bit of playing I have to agree with Toreador. If you change the code to this:
DECLARE @ VARCHAR(3) = 1952 + 03 + 11 - 2001 - 05 - 11;
SELECT ASCII(@) AS [the answer to life, the universe and prime numbers];
you get an answer of 45 which is the ascii code for "-".