A normal cycle, takes an average of 28 days. It starts the first day of the period and ends the day before the beginning of the next period. However, this is not definite and in many cases the menstruation may appear anywhere between the 21st and 45th day. Typically, ovulation happens the14th day of the cycle, while the fertile days are usually 11th, 12th and 13th. However, a premature ovulation can happen on the 7th or 8th day or likewise a delayed ovulation on the 18th or 19th day. Over the years, the period cycle is stabilized. As a result, most women can estimate their menstruation cycle. It is important once the period begins, to record the dates of your cycle on a calendar and keep track of how prompt your cycle is. This recording will prove very useful, whether scheduling your next visit to your gynaecologist, or when planning…your vacation! You can use EveryDay’s period tracker if you want to calculate when you will get your next period. If your period is still irregular, or delayed for longer than a week, it is advisable that you consult a gynaecologist. If your cycle is stabilized and is lagging behind, you should have the following in mind: pregnancy (if you’ve had sex), stress, diet or weight loss, excessive exercise, or a recent onset of a drug. In any case, a gynaecologist’s opinion is necessary.