What is the length of time between menstrual periods?
Question

What is the minimum period of purity (tuhr)? My menstrual cycle is not regular. Sometimes I do not have a period for months, sometimes it comes on time. I did ghusl following my period ten days ago, and during this time there was some light yellow spotting from time to time, but after ten days it increased and became a new period, with cramps (period pains) and the usual colour of menstrual blood. I was told to do ghusl and pray because the minimum length of tuhr (purity following the previous period) is fifteen days. Please advise me, may Allaah reward you with good, because I stopped praying, thinking that this was a period.
Praise be to Allah.There is no set minimum limit for the period of purity between two menstrual periods, rather when a woman sees the blood – i.e., menstrual blood which is “black” (dark red), recognizable and has a distinct odour – she should refrain from fasting and praying, on condition that the total number of days of menstrual bleeding does not exceed half of the cycle (i.e., fifteen days in the month). Yellowish and brownish discharge seen after the period has ended are of no significance and they do not come under the same rulings as menstruation.