One of my college classmates (at a very expensive U.S. liberal arts college) used to quip "The more you pay, the less you stay." We had two 13-14 week semesters per year (1-week break in each, Thanksgiving in the fall and mid-semester break in the Spring), with a 6-week optional January term between and 14 weeks for summer. Sticker price was $45K when I went there and is now $70k.

Minor quible, the most common system in the US has 15 week semesters for fall and spring.

Univ. of Washington had 3 quarters per year. Don’t know about now.

Oxford and Cambridge. Probably a few other old unis in the UK.

That squares with what I have heard before about UK university degrees being shorter than US degrees. What do you do with the rest of the year?

Internships. Or work, or study. Up to you. You have an informal exam when you get back and if you annoy the profs enough they'll kick you out for failing it. But that's pretty rare.

Time spent per year is roughly equivalent. UK degrees are shorter than US degrees because we spend only three years at university for a bachelors degree. Depth is similar but there's less breadth - we only study our major, so as a CS student all my classes were taught by the CS department apart from a handful of math classes.