Is the small amount of dark blood after a month from menstruation considered istihaadah (post-menstrual bleeding) or hayd (menstruation), and what is the maximum duration for istihaadah if the spotting does not stop for more than a month?

The maximum period for menstruation is fifteen days, and anything beyond that is considered istihadha (non-menstrual vaginal bleeding). A woman experiencing istihadha has the ruling of a ritually pure woman.

If the bleeding continues, and if the woman had a regular cycle before the irregularity, she should consider the days of her usual cycle as menstruation, and anything beyond that as istihadha.

If she does not have a regular cycle, but can distinguish the characteristics of menstrual blood by its color, smell, pain, or thickness, then what possesses these characteristics is considered menstruation, provided it is suitable for that (i.e., not exceeding 15 days and not less than one day and one night), and anything else is istihadha.

If she has neither a regular cycle nor the ability to distinguish, she should, by estimation, consider six or seven days as menstruation, based on the prevalent custom of women in her family, and consider herself in a state of istihadha for the remaining period.