Nutrition Before Race Day

I am doing the Tough Mudder on Saturday and was curious to know if I should slightly increase my calorie intake today and tomorrow? Right now, my suggested calorie intake without exercise is 1,200 cal / day and since I'm taking the next two days as rest days that seems kind of low.

So, I guess my question is - how do you prepare nutritionally before a Tough Mudder, Marathon, Ultra, etc.

Thanks for the feedback!