Each cycle occurs in phases based on events in the ovary (ovarian cycle) or the uterus (uterine cycle). The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase; the uterine cycle consists of the menstrual, proliferative and secretory phases. Day one of the menstrual cycle is the first day of the period, which lasts for about five days. Around day fourteen, the egg is released from the ovary. Menarche (the onset of the first period) usually occurs around the age of twelve years. Menstrual cycles end at menopause, which is usually between 45 and 55 years of age.