According to American Pregnancy, ovulation itself lasts only one day while an egg is detached from the ovary follicle. However, the entire ovulation cycle is composed of two longer phases called the follicular and luteal phases.
American Pregnancy explains that the follicular phase of the ovarian cycle can last anywhere from seven to 40 days depending on the end of the woman's period and the beginning of her ovulation. Once the egg leaves the follicle, it has between 12 and 24 hours to survive and await fertilization. BabyHopes.com provides a contrary assessment, suggesting that in some cases the egg can survive as long as 48 hours once it leaves the uterus.
The luteal phase of ovulation lasts between 12 and 16 days, from the end of the ovulation until the beginning of the next menstruation. Because these phases are entirely dependent upon the day of ovulation, the length of the menstrual cycle can vary significantly. According to American Pregnancy, ovulation can occur earlier or much later than usual if factors like stress, illness and disruption of daily life are at play. BabyHopes.com states that ovulation is most common between days 11 and 21 of the menstrual cycle in a healthy woman.