Safe period is not a continuous period in menstrual cycle. We know a woman is fertile only in the ovulatory period, and infertile in other days. And she can not has sexual intercourse in the menstrual period when she’s bleeding. So the days in a menstrual cycle except menstrual period and ovulatory period is safe period.
In safe period, a woman could has sexual intercourse and almost no chance to be pregnant. But it is not very reliable method for contraception because we cannot predict the next ovulation time precisely.
Now we consider the first bleeding day as the first day of menstrual cycle. The days before the 7th day is very safe for contraception. If a woman stopped bleeding in 5 days, she has 2 days to have sexual intercourse without condom. And the last 4 to 5 days are also very safe. You could choose these days in safe period to avoid pregnancy.
NOTICE: you must consider this article at your own risk!