If you want to be 10-12% by summer, I'd start in January. It gets harder as you go. You probably need to lose 25-30 lbs to be 10%. Assuming more than 1 lbs/week (discounting water weight loss) is probably a pipe dream, even though you'll lose more at first. And you need loco-like focus to go straight from 20 to 10.
Suggestion for optimal diet strategy:
1) Use 5/3/1 with BBB or similar high volume assistance work
2) Use
http://www.1percentedge.com/ifcalc/, use "lightly active". Subtract 25% from the TDEE and use that as your baseline cal intake.
3) Log everything you eat, at least for the first month. You can possibly guesstimate after that.
4) Take a diet break after 8 weeks, 2 weeks eating at maintenance.
5) Have a cheat meal a week if you feel like it.
6) If you're not IF'ing, refeeds are good too, both psychologically and physiologically (cheat meals not required if you do these). In fact, just follow Lyle's advice in "a guide to flexible dieting".
7) If you have social events, plan around it. Going to a huge dinner buffet? Eat very little for the rest of the day. Try to avoid the biggest calorie culprits. If I'm dieting and going to a chinese buffet, the fried stuff is out and I basically eat the cooked stuff and veggies, little to no rice.