My Sims have College Adjuster on their term lengths on an individual basis (the better their grades, the longer their terms). My Sims can go to university at any time during their teen years, and occasionally get aged down from adulthood to attend. This has led to one situation where four siblings and their mum entered university together. For some Sims, university is a massive boon and doubles their "adult" lives. For the laziest Sims (or for some who get kicked out), it's actually a penalty. The variety helps make things more interesting for me.

A viable alternative would be to use the Adjuster to make all terms for your Sims 24 hours long, then send eligible Sims 9 days before thy turn adults. Then you can use the same lengths of rotation for the university as you do for your other Sims.

I use Inteen and so all teens leave school midway through the their teenage time. What happens next depends on their aspiration, LTW, my story for them, and anything that might have happened, such as getting caught by risky woohoo. Some will go to work, some teens in well off families might spend some time "off", but those who go to Uni will go when there is 5 or 6 days left, and they return to the 'hood on the day they should be ageing up to adult. How much I actually play them in Uni varies, but quite a few get rushed through with the aid of the College Adjuster. If they don't have the skills needed for whatever they want to study they don't get to go in the first place, I can set the grades if I want, they get to have some fun. It tends to work that they don't have more days at Uni than they would back home.

The way I calculate my sims' ages, my uni students are 4 years older than their non-uni counterparts. I can't really explain why this doesn't bother me, but I'll try. Somehow, I look at it as, uni gives these sims a little more maturity and certainly more skills than they would otherwise have in the main hood, and as a result they're more 'mature' somehow than their main hood counterparts. This is pretty much the opposite of how I think this works in real life, but sims being what they are, every additional skill point helps XD

I use Inteen and have Sims leave for university the day they finish school. If they complete their degree, they're only a day or two younger than those who went straight to work after school, so I can interpret that as them being slightly less mature - although those going to college might get played twice in one rotation, depending on where they're moving from and going to afterwards, so often they end up perfectly synchronized anyway.

The only problem arises if they can't afford to finish college. In that case, I can either ignore the age difference or leave them unplayed on a uni lot until they reach the right age compared to their peers (most importantly, their intended spouse). Another option would be to have them work for a few days before going to college for one or two semesters at the last minute, but that's more difficult to keep track of.

Uni-bound teens leave just before they age up to adult, but I then deduct their YA years from the adult lifespan. I play with Almighty Hat's aging mod; losing 16 days off adulthood isn't much when one starts with 112. Even a sim with a few Academic Probation semesters thrown in doesn't lose that much extra - I have 48hr semesters and keep a running tally of how many days I need to deduct.

The biggest issue with that method (besides the need to keep notes) is using Inteen as well, if a sim has a baby on campus, it's vital I make a note of their birthdate, as final exams can result in them losing a day. If they hit the age they'd be when Mum is due to graduate but the timer on the final exam will slip past 6pm, then I have to stop their aging temporarily with BO's mod. This happened with Roxie Sharpe's triplets... twice if I remember rightly!

I consider the University as something apart from the rotation, like Orphalesion mentioned.

When the main hood rotation ends, I play all the households in university hood until everybody graduated, so it won't feel that 4 years lasted an eternity and the graduated adults will be about the same age as the ones who skipped college. To make it less of a chore, you can use this mod which reduces the semesters duration.