The 13-Moon calendar functions according to a Year-Bearer system passed down by the Chilam Balam Jaguar Priests of the Lowland Yucatec Maya which assigns every new year one of 4 solar seals - either Red Moon, White Wizard, Blue Storm, or Yellow Seed. These colors correspond to the 4 directions, East through South. Every year also receives one of 13 tones.
For example, July 26, 2001 began Yellow Solar Seed Year (9 Seed), and July 26, 2002 begins Red Planetary Moon Year (10 Moon), and July 26, 2003 begins White Spectral Wizard year (11 Wizard.) This harmonic pattern of 4 solar seals cycling with the 13 tones ensures a perfect cycle of 52 years in which no two days repeat, until the completion of the 52 year round (a cycle of 18,980 days called Tunben K'ak, the Binding of the Years).