I was just doing some thinking tonight, though I honestly can't remember what exactly brought me to this.  I do know that I was pondering Bungie's knack for playing around with numbers, and I thought "Hey, is 117 a prime number?  No, it isn't; it's the product of 9 and 13."  So, since the MC (despite having a known birth year) does not yet have an official birth date, and I haven't heard of any conspiracy theories about it, I've decided to grant him a D.O.B.: September 13, 2511.  I admit that 3 x 39 = 117 as well, but there is no 39th day of March.  If this information has been somehow undisclosed, or someone else has already done this, I request that you let me know.

P.S.  Now please, no one go off on some "OMFG! I know when Master Chief wuz born!" rage. That kind of thing just ends badly.  I also ask that you not quote that line in the comment space either.  Sorry, but I'm too tired to deal with it.