Step-by-step calculation procedure:
The 3-step procedure below is provided so that you can test the accuracy of the
calendar yourself - fast, easy and error-free. We suggest you start with family and
relatives and then check with friends. The most essential condition for getting
relevant statistics is that you know the circumstances of each birth.
Pregnancies where fertilization took place in a laboratory should not be taken into
account, since the calendar is predicting the actions of natural processes that take
place in the female ovum. In other words, only naturally induced pregnancies are
meaningful for the tests.
Find out the date of conception.
If you don't know the date of conception you can easily calculate it, provided that
you know the circumstances of the pregnancy. Usually babies are born around the
expected (normal) date, but sometimes births take place weeks or even months
before and sometimes weeks after. Whenever that is the case, you need to
compensate for that. If for example a baby was born 2 weeks early, you should add
14 days to the actual date of birth, in order to find the "normal" date.
When you have established the "normal" date of birth, simply count nine months
backwards in order to arrive at your estimated date of conception. You can also use
the conversion table below, which relates 'month of birth' with 'month of conception'.
Find out the mother's age at conception.
a. Substract 'mother's birth year' from the 'conception year'
b. Substract one year if the date of conception is before the mother's birthday
The result of this calculation is the mother's age at conception.
Consult the calendar.
Make the gender prediction by cross referencing the mother's age at conception
with month of conception.