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How does the Maya tzolkin calendar use 20 day-signs within a 260-day cycle?

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What's your sign? — astrology Zodiac wheel showing the 12 astrological constellations or signs from an illumination of the poem *Breviari d'Amour*, Catalan (Spain), late 14th century; in the collection of the British Library.

The Tzolkin, or sacred divinatory calendar, functions through the simultaneous meshing of two distinct cycles to create a 260-day period.12

The calendar operates by combining an ordered series of 20 named day-signs with a sequence of numerals ranging from 1 through 13. Because these two cycles run concurrently, each day is identified by a unique combination of a number and a name (for example, 1 Imix, 2 Ik, and so on). This mechanism ensures that a specific combination of a numeral and a day-sign only repeats once every 260 days ( $13 \times 20 = 260$ ).1

In the context of divination, the Maya believed these days possessed a specific, fateful character. While the exact methods used to interpret these omens remain largely unknown to modern scholars, the Tzolkin was central to their religious and astrological practices, serving as a tool to understand the nature of time and its influence on human events.12