Muwan is the fifteenth of the nineteen periods of the Haab, the 365-day Maya solar calendar. Recorded here by its Yucatec name, Muwan, which names a bird, generally taken as a screech owl or a mythological sky-bird associated with rain, the month is known from the colonial sources and, in its glyphic form, from the Classic inscriptions. Like each of the eighteen full months it counts twenty days, and a Maya date names a day by its position within the month alongside the interlocking Tzolk'in day sign and number. These are the features of the Maya solar calendar, built of eighteen twenty-day months and a closing five-day period, which meshes with the 260-day sacred count in the fifty-two-year Calendar Round of Maya timekeeping.
Muwan, the fifteenth month, takes its name from a bird, generally identified as an owl or a related nocturnal raptor associated in Maya iconography with the underworld and with omens, appearing as a named entity, the Muwan bird, in Classic-period art and inscriptions independent of its use as a month name. Owls and related birds carried a broadly ill-omened association across Mesoamerican traditions generally, a pattern that recurs in the unrelated Aztec belief that an owl's call foretold death, though the two traditions' specific symbolism should not be conflated as though they shared a single source. Diego de Landa's colonial account does not describe a uniquely documented ceremony tied to Muwan beyond the general pattern of observance recorded across the calendar's later months.