You might find it interesting to get some graph paper and start keeping a chart of the calendar date
in relation to your cycle date
. Label across the top, 1, 2, 3, 4, 5 etc. (the cycle days) as headings, and under the headings such as at the "1," write what day it is when your period begins, i.e., 8/12 or whatever, and keep filling in dates under the 2, 3, 4, 5 etc. headings until your next period comes. Then list ITS date as Day 1 on the next line.