How is the waiting period (iddah) calculated for a woman who forgot the day of her divorce, knowing that it is most likely less than three months and has already exceeded fifty days?

Scholars have not found specific rulings concerning forgetting the day of divorce. What appears evident is that a woman who forgets it should investigate and act upon what she believes to be most probable. If doubt remains, she should base her decision on certainty, following the precautionary approach adopted by jurists in many cases related to the 'iddah (definition) (waiting period). The 'iddah of a woman varies according to her situation: for a young girl and a woman past childbearing age, their 'iddah is three months; for a pregnant woman, it is until she gives birth; and for a menstruating woman, it is three menstrual cycles.