Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km (18,000 ft) of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases.
Having irregular periods is very common. I see them in my practice all the time. The causes can range from something insignificant to something that requires treatment. For example, if you're a teen, your body's hormones can fluctuate and take some time until they find a balance.
While 3-5 days is most common, anywhere between 2 and 7 days is considered normal. See your doctor if your period lasts longer than a week or suddenly changes from what's regular for you.1  Previous. 2  Continue.n young girls and teenagers, periods are commonly irregular and have cycles ranging between 21 and 45 days. Keep track of your periods on a calendar (which can help you and your doctor determine what pattern is normal for you). 1  Previous.