I got this from one of the threads. Its very easy to follow:
numbers on the left side are onset of menses while numbers on the right side inside the parenthesis are unsafe period
1 (9-1
2 (10-19)
3 (11-20)
4 (12-21)
5 (13-22)
6 (14-23)
7 (15-24)
8 (16-25)
9 (17-26)
10 (18-27)
11 (19-2
12 (20-29)
13 (21-30)
14 (22-31)
15 (23-1)
16 (24-2)
17 (25-3)
18 (26-4)
19 (27-5)
20 (28-6)
21 (29-7)
22 (30-
23 (31-9)
24 (1-10)
25 (2-11)
26 (3-12)
27 (4-13)
28 (5-14)
29 (6-15)
30 (7-16)
31 (8-17)
madali lang yan! ONSET OF MENSES IS THE DAY WEN U START UR MENS, UNSAFE PERIOD yan yung date na di ka dapat pagalaw sa partner mo, rest of the date is ur safe period.