There really is no set way to get the gender you want. Even having scientists seperate sperm that they think will be male or female doesn't 100% give you a boy or a girl.
Conception calendars are fun to look at and it's neat when it's a coincidence...but it's just that. A coincidence.
To add to that, I actually know a friend of mine who has tried for a girl for 10 years. She has 5 children. All boys. She tried everything, even the sperm seperation. No luck.