how to calculate safe period

9:49

5:15

12:55

5:30

9:45

2:55

15:11

15:13

14:15

1:44

6:17

کوتاه

11:35

6:39

3:28

3:34

2:01

5:01

3:05

5:53

5:56

13:00

3:24

3:17

8:48

8:29

5:04

4:08

21:23

14:15

9:59

4:15

2:53

1:36

1:29

10:54

11:19

11:07

5:15

2:40