Menstruation is the technical term for getting your period. What happens during the typical 28-day menstrual cycle? Day 1 starts with the first day of your period. Menstrual flow might occur every 21 to 35 days and last two to seven days. During each menstrual cycle, an egg develops and is released from the ovaries. The length of the menstrual cycle varies from woman to woman, but the average is to have periods every 28 days. The four phases of the menstrual cycle are menstruation, the follicular phase, ovulation and the luteal phase.