The marketplace is open from Oct. 1 to March 31, 2014. If you enroll by December 14, your health care will kick in Jan 1. If you enroll from Dec. 14 to Jan. 31, your insurance kicks in on Feb 1, 2014. If you wait until February to March 31, your coverage won’t begin until April. And if you don’t sign up, you will have to pay a penalty.