The Mayan Haab’ Calendar Design The Mayan Haab' Calendar comprises eighteen "months" of twenty days each, plus an additional period of five days ("nameless days") at the end of the year known as Uayeb'. This gives a year length of 365 days The Haab' was first used around 550 BCE with the starting point of the December Winter Solstice. The Haab' was the foundation of the agrarian calendar and the month names are based on the seasons and agricultural events. For example the thirteenth month, Mak, may refer to the end of the rainy season and the fourteenth month, K'ank'in, may refer to ripe crops in the fall. The names of these months are: Pop, Uo, Zip, Zotz, Tzec, Xul, Yaxkin, Mol, Ch`chen, Yax, Zac, Chen, Mac, Kankin, Muan, Pax, Kayab, Cumku, and Uayeb. This unique design has the Mayan death god called Yum Cimil featured in the center. He also could be called Ah Puch, the god of the Underworld. His body is predominantly skeletal. His adornments are likewise made of bones. Yum Cimil has also been represented with a body covered with black spots (decomposition). He also wears a collar with eyeless sockets. This adornment was the typical symbol for the Underworld.