It's simple! Just record the time of her monthly whim! See if there is any advance or delay, for example, when will it happen this month and how many days will it last? When the onset of next month approaches last month, make preparations in advance to observe whether the onset of this month is basically the same as last month.

Supplement: The menstrual cycle is calculated from the first day of this menstruation to the first day of the next menstruation.

The average period is generally 28-30 days. 2 1-35 days is the normal range of menstrual cycle.

The fluctuation of menstrual cycle is influenced by many factors, such as emotional changes, health status, diet and drugs, changes in living environment, pregnancy and so on. Usually, it is normal to advance or delay the menstrual cycle within one week.