A lot of girls just starting their period will experience an abnormal period. I still only get my period every couple of months. Not all women get their period every 28 days. I certainly don't. It can be affected by hormones, birth control, stress. ect.
28 days is the average cycle but it is normal if it is shorter or longer somewhere around 22 - 36 days is still considered normal. If you are concerned as always, a doctor's opinion is best.
Like Jannypoop said, it's the normal cycle, though mine is usually a few days early/late, to a week late. If you experience a longer days around or a few weeks then contact your doctor.
I get mine at different intervals, sometimes I'm up to 10 days late.
I do, because mine are controlled by hormones, but others vary.
My friends girlfriend gets its every 2 months o_O
*can still be considered
