- last post: 01.01.0001 12:00 AM PDT
Hmmmm good question, my guess for the 12 hours part is that Cortana just learned about Halo and its technology
I think she didn't activate it because she was already in the clutches of Gravemind, I think that the last scene at the end of the credits is something that happened previously, but is just showing it then due to time