I graduated from my high school a year ago. I haven’t applied to any universities. Is it going to affect my acceptance chances?
Nope. Schools like gap years. It means a more mature student for them and hopefully a more focused learner. Here’s Harvard’s comments on gap years: https://college.harvard.edu/admissions/preparing-college/should-i-take-time
Gap years are common. If you have done something worthwhile in that year off from school, it could even help.
No. Sometimes, it even looks better.
A gap year look good if you’ve done something constructive in that period, like: a job, travel, study, community service, worked on a project, etc.
A gap year looks bad if u have done nothing but sleep in late and play video games.
Harvard encourages students who have already been accepted there to take Gap Years.
That is a far different scenario than what the OP is asking.
This is from the first paragraph of the above mentioned article.
“Harvard College encourages admitted students to defer enrollment for one year to travel, pursue a special project or activity, work, or spend time in another meaningful way.”
Gap years are great when you arrange them ahead of time (AFTER acceptance, defer), not just let a year go by and then join the party. It depends on what you did in your gap year and why you didn’t apply as a senior.
I am from Nepal and I volunteered in a remote school devastated from earthquake this May. I hope it helps. 
Gap Years are not just for students after they’ve been accepted somewhere. Harvard encourages it in students who have been accepted - but also in students who apply for admission after taking that year off, as do many schools.
““Occasionally students are admitted to Harvard or other colleges in part because they accomplished something unusual during a year off. While no one should take a year off simply to gain admission to a particular college, time away almost never makes one a less desirable candidate or less well prepared for college.” (Noted directly from Harvard’s website; not a direct quote from Fitzsimmons.)”
In fact, the Gap Year experience often changes a student’s goals and objectives significantly enough that it may impact where they decide to apply. The Gap Year Advantage is a terrific resource for anyone considering doing a gap year. Here’s another resource (complete with quotes from admissions directors) in support of gap years:
http://blog.winterline.com/7-quotes-from-college-administrators-in-strong-support-of-gap-years
Gap years are more common than in the past in the US. Should not be an issue.
Gap years are not unusual any longer…and as many have mentioned if you put your year to good use, it can actually be a strength.
Gap Years are still unusual enough in the US to raise eyebrows and generate the ‘but what if they don’t want to go back to school’ question from anxious parents. (Statistically 90% of gappers do go to college). I couldn’t find statistics on what percent of US students take a gap year, which indicates how unusual it still is. In our local affluent high school, only one kid we knew or heard about took a gap year in any of the 6 years that my kids were there - a school of 2,500. That’s not to say that every kid went to college. But so few made the conscious decision not to attend college for a year while doing something else and then applying (or deferring year after they had applied and were accepted) that it wasn’t considered a viable option. Of course, our school is 40% Asian, so that might be part of it - Gap Years aren’t typical in most US Asian communities. But the fact remains that this is something that many students would benefit from. (And no, we had no luck at all convincing our kids to do it although we tried. One did end up taking time off during college, but that’s not quite the same thing.)