It is completely normal for menstruation to start two days early. The timing of menstruation in women is mainly regulated by the endocrine function of the ovaries. The function of the ovaries is affected by many factors, such as sleep time, diet, sports, mood swings, environmental changes, study and work stress, etc., which can affect the endocrine function of the ovaries to varying degrees, making the time of menstruation appear earlier or later, and it is normal for menstruation to come earlier or later than a week. You should pay attention to good lifestyle habits, relax and not to be overly stressed, rest on time and not to stay up late, eat a balanced and nutritious diet, and not to be overly dieting or gluttonous.