The Chinese developed the perpetual calendar wan-nien-li in three distinct ways: through mathematical calculations, astronomical observations, and philosophical insight. Through these methods, the ancient Chinese were able to create a calendar that was consistent with their beliefs about time and the universe.

First, mathematical calculations were used to develop the system of intervals in which each month and day fell within a cycle. This enabled them to ascertain exactly when certain events would happen based on certain dates and times throughout each year. The common annual cycle was based upon 12 months of 29 or 30 days in length, while an additional five intercalary days (known as liu-yue) were added to even out any discrepancies between solar and lunar cycles during each year. By carefully calculating these different values, they were able to determine the exact date for any given day of the year within this system.