It seems to have ended up here now!
I'm not a law student, but having a quick look at their course summary I think I can answer these questions
Durham doesn't actually work on a semester system really, we have 3 terms but for most modules there's essays due throughout the year, then exam(s) in the summer term. We only have teaching in term 1 and 2, and then revision beyond that.
On a typical course you'll take 6 modules per year and you'll take them over both terms. Some courses, such as maths, do half modules which only last one term, but it doesn't seem like law does.
In first year you'll be on all core modules, so everything is scheduled for you. In future years you choose some modules beyond the compulsory ones, but your schedule is set by which modules you choose.
For almost all modules, exams will take place in the 4 week exam season in May/June, some modules may have exams outside that period, but it's not typical. When they're outside that period they can be pretty much any time though, which isn't very helpful
I've had some just before the Christmas break, some just after, and this year we have one in April, so after Easter but before the main exam season.
As I've explained, we don't work on a semester system really, so it's difficult to compare. There's advantages and disadvantages to having all our exams at the end of the year, but I think doing a module across an entire year allows you more time to understand it and actually go into depth compared to maybe quickly touching on lots of things in little depth. It also means you tend to have less revision over Christmas, which no one complains about!
Hope that answers some of your questions