The highly complex Chinese calendar is a combination of a solar and a lunar calendar, calculated separately and then synchronised. How is this done? By adding an extra lunar moth also called a leap or intercalary month. This 13th month is added approximately every three years to bring the two cycles back in sync. Finally, the Chinese calendar divides the solar year into 24 terms, or breaths, which symbolise the agricultural calendar.
The intercalary or leap month appears according to precise rules and is assigned the number of the month that preceded it. The calculations are complex but serve to keep track of the seasons and to set the Chinese New Year at the arrival of spring, which varies between between 21 January and 19 February in our calendar.