Woo four days for 2x, sounds fun. There is some hot time this weekend and you can see it in the Event Tab (Shotcut-Key: V) ingame.
I would make note of it, but you never know if Nexon will change the prizes or what. So for now this is the news you get lols.
January 10-11th, 2013
Pacific: 3 PM – 7 PM
Eastern: 7 PM – 11 PM
January 12-13th, 2013
Pacific: 2 PM – 4 PM
Eastern: 5 PM – 7 PM
This event will stack with EXP coupons, so you could use a 2x EXP Coupon from the Cash Shop to get 4X EXP for those days!