Deadlines are going to control your whole application process. UCAS is easy, as all of your five applications are due to be submitted on the same day.
US college applications, and many other international universities, are more complex. So do your research. A January deadline gives you a lot more time to create your best application than a November 30th deadline.
This is a date you need to stick to.
e.g. IELT's, BMAT, UCAT, SAT's, ACT's...