CALENDAR METHOD of Birth Control

* Before you can use the calendar method as birth control, you need to keep track of the length of your menstrual cycles for at least 6 periods. 

* Mark the first day of your period (this is day 1). Then mark the first day of your next period. Count the total number of days between each cycle (the number of days between the first days of each period).

* You must chart at least 6 cycles, but charting a few more months is even better.

If all of your cycles are shorter than 27 days, the calendar method won’t be accurate for you.

- Predict the 1st Fertile day:  

To predict the first fertile day (when you can get pregnant) in your current cycle:

• Find the shortest cycle in your past record. (ex. 26)

• Subtract 18 from the total number of days in that cycle.

• Count that number from day 1 of your current cycle, and mark that day with an X. (Include day 1 when you count.)

• The day marked X is your first fertile day.

* For example: if your shortest cycle is 26 days long, subtract 18 from 26 — you get 8. Then, count 8 days starting from day 1 (the first day of your period). If day 1 was on the 4th of the month, you’ll mark X on the 11th. So the 11th is your first fertile day of this cycle — you should stop having vaginal sex on this day or start using another method of birth control.

- Predict the Last Fertile day: 

To predict the last fertile day in your current cycle:

• Find the longest cycle in your record. (ex. 30)

• Subtract 11 from the total number of days in that cycle.

• Count that number from day 1 (the first day of your period) of your current cycle, and mark that day with an X. (Include day 1 when you count.)

• The day marked X is your last fertile day.

For example, if your longest cycle is 30 days long, subtract 11 from 30 — you get 19. Then, count 19 days starting from day 1. If day 1 was on the 4th of the month, you’ll mark X on the 22nd. So the 22nd is your last fertile day of this cycle — you can start having unprotected sex the next day.

The days between the first fertile day and last fertile day is called the 'fertile days' zone in which when we have sex there is lot of possibilities to get pregnant. Apart from which is very less to zero possibility. Using this, we can have safe sex unprotected.