yu count the first day yu start "af" to the nxt. to determine how many days
I do understand, however I was told that in order to calculate your ovulation. You need to first calculate your cycle thus from the day you stop your period until the next time you start. But how do you know when you end in order to calculate the time in between?
whenever you are asked this by medical staff they are referring to the "first day of your last period". It is not important to know when the last day was, as that will vary from woman to woman.