If somebody still needs a hint when to do this in the year 2012, I started doing this at 8 PM local time on GMT +2 zone Friday (Finland), and it unlocked in 10 minutes. Switching between Friday and Saturday.
Just look at this map and work out the time difference with it so that you know when to do it. My zone is the +2 in the map and it's not hard to figure your correct time with the map.
100k - 24.8.2011 | 200k - 2.12.2012 | 300k - 1.12.2013 | 400k - 24.3.2015
My top 10 shooter completions: Gears of War 3, Max Payne 3, F.E.A.R., F.E.A.R. 2, F.E.A.R. Files, Rainbow Six Vegas, Warhammer 40k Space Marine, Gears of War 2, Legendary, Left 4 Dead 2 (Realism Expert legit Dead Center & Hard Rain) | XBA shooter leaderboard: 141,727g (8th)
Incoming: Halo: MCC?