FYI for midnight launch you can change your clock and still do it ONLINE for the datestamp. Just change your timezone to one that's about to strike midnight so you can stay on live and put a timestamp on the achievement.
HALO:MCC >>>>>>> Interested in Online Customs, Squadmates for Ranked, and Co-Op Campaign. I am on 6am-4pm GMT on my nights off (Midnight-10am US Central). Copy this signature with your play times so we can populate our friends lists with fellow Halo:MCC players BEFORE launch!! If you add me do it on XB1 please; my 360 friends list is nearly full.