What is the ruling for a woman who knows the number of days of her period but not the specific time within the month?
Chapter on Menstruation
Al-Mughni
Book of Purification
Primary text
If a woman knows the number of days of her period but is completely ignorant of the timing, she observes that number of days each month. This observation is either counted from the beginning of the month or determined via estimation, based on differing scholarly opinions.
Supporting text
If she knows the time frame, such as the first ten days of every month, but not the exact number of days, she observes the known duration within that known time frame. If the known duration exceeds half of the assumed period length, the excess over half is counted as definite menstruation, and the remaining days are observed through estimation in one view, or counted from the beginning of the known time frame in another view.