The Chinese birth calendar is a gender prediction tool for expectant parents. Alternatively, you can use the date of conception to narrow down the gender of your child. Typically, the date of conception is calculated by subtracting days from the expected due date. The Chinese birth calendar purportedly traces its history back hundreds of years in China. The calendar was a closely-guarded secret by emperors of the Qing dynasty. They did not show the chart to others, but kept it for their own predictions.