My universities all used the semester system (Fall, Spring, with the option of a May Mini-mester, a Summer I, and a Summer II.) A full-time undergrad usually took between 12 and 18 semester hours. You needed to get special permission to take more than 21 hours. A language class or a science with a lab is going to be 4 hours; PE is 1 hour; most other classes are 3 hours. You take general classes towards your degree, and basic classes in your major, in your freshman and sophomore years. By the time you get to your junior and senior years, you're taking classes that are more advanced within your major, as well as wrapping up your degree requirements. So 1xxx courses are freshman/basic classes, 2xxx courses are sophomore/more advanced classes, and 3xxx/4xxx-numbered courses are going to be limited to people pursuing that major. The second digit shows how many hours' credit you get-- if it's x1xx, it's 1 hour's worth of credit, x2xx is 2, x3xx is 3 hours' credit; x4xx is 4. So, for example, in my junior year, and I'm majoring in Archaeology, I might take Geography 1300 (towards my degree), Political Science 2302 (towards my degree), English 2301 (towards my degree), Archaeology 3351 (towards my major), and Archaeology 3359 (towards my major). So I have one freshman-level course, two sophomore-level courses, and two junior-level courses, and I'm taking a 15-hour courseload. So if I've structured my schedule correctly, I would probably have three classes MWF, and two classes TTh. My MWF classes would probably each be an hour long, and my TTh classes would each be 1.5 hours long, so that I spent-- you guessed it!-- three hours a week in each class.
In the case of a four-hour science with a lab, for scheduling purposes, it was treated as three hours of lecture, plus 1 hour of lab each week. In the case of a four-hour language... I don't remember there being anything different about the scheduling from a normal three-hour class, although there was certainly way more time spent after class on homework. In the case of a one-hour PE class, we also spent the normal three hours a week, although we didn't get three hours' worth of credit.
In real life, it's usually best to plot out all the courses needed to graduate with your degree and your major, and then make sure you sign up for them evenly, so you have a good mix of easy classes and hard classes, degree-specific classes and major-specific classes, and you earn your prerequisites early on, so that you don't have to be delayed in signing up for the more advanced stuff. You don't want to end up taking Greek and Latin in the same semester (unless you have superpowers), and you don't want to spend seven semesters moseying along with only 12 hours each... and then be surprised, "Why is everyone graduating without me?!" and realize that you need 145 hours to graduate, and you still have 61 hours left to earn.
So, that's pretty ordinary for a lot of US universities, both public and private. However, as was pointed out above, UCLA does things differently, with the quarter system. For the 2018-2019 school year, the dates run: fall (Sept 24-Dec 14th) / winter (Jan 2-March 22nd) / spring (March 27-June 14th) / summer. They also seem to have five different summer sessions: your choice of a 6, 8, 9, and 10-week Summer A (they all begin on June 24th, but they have different ending dates), as well as a Summer C (Aug 5-Sept 30th).
Rather than measuring things in hours, they call them "units" at UCLA. Just a quick glance at their course catalog shows there isn't a correspondence between how many units something is, versus how much time you spend in that class. So if I'm an Anthropology major, and I pick up Human Evolution or Animals in Anthropology or Culture and Society, they're each worth 5 units, but Human Evolution consists of 3 hours of lecture, and 1 hour of discussion; Animals is a three-hour seminar; and Culture and Society is three hours of lecture, one hour of discussion, and fieldwork.
So-- I think it's one of those things that's like setting your story at Oxford or Cambridge. The people who have been there will say, "Wait, that's not how things work here--!" So the easy path is, "I want to create a fictitious university where I can make up my own rules".
But if you're set on it being UCLA, it's good to be accurate, so you might find some sort of UCLA message board, and make a post. "Hey, I'm writing a story. Can a current UCLA student share what this quarter's schedule looks like for them?"