As someone who loves to have an organized life, I ironically dislike having a structured work schedule. I even dreaded going to high school because of having to wake up so early for 5/7 days of the week. If I major in Computer Science, will I have to face the sadness of having to wake up early and repeat the same routine every day of me life?
P.S. I’m a night owl, so if I don’t have to work mornings at all I would be the happiest person alive.
It depends on the company. Some allow flexible schedules. Also, if you end up more in an IT type job (as a fair number of CS majors will), you may work more nights and weekends than you care to. Often maintenance and project deployments have to take place outside 9-5 windows. Or you are on calls with offshore resources at crazy hours.
Being a freelance developer can solve the 9-5 problem - pick your own projects, work your own hours. That’s obviously sacrificing some stability though.
It’s also worth noting that many tech companies have very shifted clocks, so at some companies coming in as late as 11 AM would be seen as perfectly fine. It would mean staying until 7PM though, etc.
I’m a night own but I actually don’t find the 10-6 (no one in my office comes in before 9:30 or so at least) to be too bad. If you had asked me if it would have been okay in high school, I would have told you that you’re crazy. Your internal clock is still shifting, so give it time.
Long story short - for a night owl, not many other careers will offer the flexibility of CS in terms of hours, so absolutely don’t shy away because of that.
I’ve never worked 9-5, partly because that’s 7 billable hours. 7 billable makes you an easy mark to get out hustled
Some jobs are more regular than others, and every couple of years I’ll drift into a position with a 45 (billable) hour week. Even those take a lot of discipline to get your stuff done and get out at a reasonable time.
Rarely do I work more than sixty, but it happens. The week we picked up a contract to support Indy car engine controllers, I recall one day that went from 9AM through 7PM the next day, but that was unusual too.
No matter what you do, you’ll have to out hustle the next guy. It’s a lot easier if you love it. Even with the sometimes nutty hours, I’d still do it for free. I need to take the money though, because HR needs to remember that they care. 
I have encountered some people working in software whose typical work hours were 9pm-5am.
Me too, when times are good.
They go first during the layoffs I’ve experienced. Maybe other places, other industries are different.