The term luteal phase is named after the corpus luteum which is a structure that grows on the surface of the ovary where a mature egg is released. This structure produces progesterone and plays a major role in pregnancy. The days past ovulation period is called the luteal phase. It is also known as ‘DPO’. This phase starts at ovulation and ends on the day before your next period and generally lasts for 14 days. For your pregnancy to be better supported, the luteal phase should be at least 10 days.
It is the length of the luteal phase that determines the ovulation time. There are many factors like stress; illness etc that can have an impact on your menstrual cycle but the luteal phase usually remains constant in most women. If you do not know the length of your luteal phase you can assume it is 14 days which is the average for most women. Since this is usually constant, the ovulation time can be estimated by calculating the difference between the length of your luteal phase and the length of your menstrual cycle. This is the same formula that the ovulation calculator uses to determine the optimal time for ovulation.
The only best and appropriate way to estimate the accurate length of your luteal phase is through certain hormone-specific blood tests.