Lets start with the basics - below you'll find links to term dates, which is usually when people aim to be in Brighton to study! To build on that, you'll typically get a full course list near the start of a term with times and dates for lectures, labs or seminars.
Grab a wall planner - usually you can get one from Fresher's Fair for free from the student union, but if you aren't able to, you can often pick one up for a couple of quid or grab a cheap wall calendar. The Uni made one is slightly better because it will come with important dates pre-printed on it, but not essential.
If you've got Gmail (or even if you haven't) you can set up a Google Calendar for free, or if you've got Microsoft Office (there is a cheap version for students and you'll probably need some sort of office software, though Open Office is free!) you can use Outlook as an easy place to manage a calendar. You can sync either or both of these to your phone and for the sake of 30mins at the start of term, you can save a lot of stress and headaches! You can also share Google Calendars with friends or coursemates if you're working on something together, or if either of you have forgotten something.
Term dates vary a bit between the two Unis, though mostly they are split into 3 terms of 10-11 weeks, with breaks of around 3-4 weeks between and the summer off. The terms mostly overlap +/- a week on either side, so most of the students are around at the same time. Some courses in Brighton Uni work on a 2 semester system, which are around 4 months long and almost back-to-back from October to June.