You had your period on the 15th of last month and you will have your period around the 12th-15th of this month. Generally speaking, the time of menstruation has its own cycle, usually about (28-7～28+7) days, everyone’s menstrual cycle is different, usually women with regular menstrual cycle, the menstrual cycle will be around 28-30 days, so if you had your period on the 15th of last month, you will probably have your period around the 12th-15th of this month. The menstrual cycle is a cycle of menstruation that occurs after a woman enters puberty. It is the process of cyclical proliferation and shedding of the female endometrium, when the endometrium proliferates to a certain degree, changes in hormone levels in the body will cause vascular spasm, ischemia and necrosis of the endometrium, and rupture of blood vessels and fragments of shedding of the endometrium are discharged out of the body through the vagina, thus forming the menstruation. During menstruation, usually women’s resistance will be reduced, easy to get cold and flu, so women must pay attention to keep warm and rest more during menstruation.