I went to the test center to register toefl test today. there is no room at the end of December, but there are still some in the middle of the month.

If you write by computer, you can get your score after two weeks, otherwise you need to wait about 5 weeks for your score. If you believe you can get the score which is higher than the prerequisite of the universities you'll apply, it's not late to take the test at the beginning of next Jan.