The chart predicts a baby's gender based on the mother's lunar age (age based on the Chinese lunar calendar) at conception and the lunar month of conception. These two factors cross-reference to suggest whether the baby will be a boy or a girl.

Origin: The chart supposedly dates back over 700 years to the Song Dynasty in China. Legend has it that this chart was found in a royal tomb near Beijing and is currently housed in the Beijing Institute of Science.

Usage: To use the chart:

• First, determine the lunar age of the mother at the time of conception.
• Then, find the lunar month during which the baby was conceived.
• With these two pieces of information, consult the chart. The intersection of the mother's age and month of conception will indicate either a boy (often marked with 'B' or blue) or a girl (often marked with 'G' or pink).

Accuracy: The accuracy of the Chinese Gender Chart is a matter of debate. While many claim that it has worked for them or people they know, scientifically there's no evidence to suggest that it has a consistent predictive accuracy above 50% (which is the same as random chance).

Cultural Note: In some parts of the world, the chart is taken quite seriously, and it's sometimes used by couples hoping to conceive a child of a particular sex.