How did the 260-day ritual cycle combine with the 365-day year in the Mesoamerican calendar?

In Mesoamerican civilizations, the 260-day ritual cycle (often called the Tzolkin or tonalpohualli) and the 365-day solar year ran concurrently, meshing together to form a larger cycle known as the Calendar Round.123

This system functioned as follows:

• The Cycles: The 260-day cycle consisted of 20 named days combined with the numbers 1 through 13. The 365-day year was divided into 18 months of 20 days each, plus a final period of 5 "nameless" or unlucky days.1234
• Synchronization: Because these two cycles ran simultaneously, a specific day designation—comprising both its ritual cycle position and its solar year position—would only recur every 18,980 days.13
• The 52-Year Period: This 18,980-day interval is equivalent to 52 years of 365 days. At the end of this 52-year period, a designated day would return to the same position in the solar year, completing the Calendar Round.13

This interlocking mechanism allowed Mesoamerican peoples to assign each day a unique designation, providing a precise way to track time for religious, divinatory, and historical purposes.123