It may be seven to 21 days from the beginning of a woman's period to ovulation. Then there are usually 14 to 16 days from ovulation to the beginning of the next period. During puberty, it's not unusual for three, four, five, or six months to go by between periods. Eventually, they happen every four or five weeks. Sometimes there is a spotting of blood between periods.
Some women know when they are going to have their periods by the way their bodies feel.
Some women keep a record of their periods on a calendar to become more familiar with their cycle. Some girls and women may have physical or emotional discomfort up to two weeks before menstruating. Usually mild, PMS happens in fewer than half of all women. Women use sanitary pads or tampons to absorb menstrual flow. Every package has instructions.