Whether or not the day after your period is a safe period depends mainly on the duration of your period, and generally the first week of your menstrual cycle is a safe period.
The safe period is not calculated from the first day of menstruation, but from the first day of menstruation. If the period lasts for 3 days, then the period is safe for 4 days after it stops. If the period lasts for a week, then the day after the end of the period is not a safe period, but a fertile period.
Ovulation usually occurs in the middle of two menstrual periods, and a week or five days before or after ovulation is considered an fertile period, when ovulation can occur at any time. Safe periods are around the first and last week of the menstrual cycle, but they are not 100% free of pregnancy. Ovulation may occur earlier or later, and sperm can survive in the woman’s body for up to three or four days.
Safe period contraception is not 100% effective in clinical practice, especially for patients with irregular menstruation, and should not be relied upon. If you do not have plans to have children, it is recommended that you take proper contraceptive measures.