Having irregular periods can mean a variation in the number of days you have your period or that your period arrives early, late or even skips a few months. A menstrual cycle is counted from the first day of a period to the first day of the next. The average menstrual cycle is 28 days, but this can vary from woman to woman, and month to month. Actually, most women will experience irregular bleeding at some point in their life. A period showing up unexpected or delayed does not always mean something serious is going on. But your period showing up whenever it wants can be stressful.