What is the name of the 365-day Maya solar calendar?

The 365-day Maya solar calendar is called the Haabʼ.

The Haabʼ consisted of 18 named months, each containing 20 days, for 360 days, followed by five additional “nameless” days called Wayebʼ. The Maya generally numbered month days from 0 through 19, producing dates such as 0 Pop or 14 Yax.

Wayebʼ was regarded as an especially risky period. Later accounts describe people staying indoors and avoiding activities such as washing or combing their hair because the boundary between the ordinary world and the supernatural realm was thought to weaken.

The Haabʼ was not a leap-year calendar. Its 365 days were about 0.2422 days shorter than the tropical year, so its dates gradually drifted against the seasons. It worked alongside the 260-day Tzolkʼin; together, the two cycles formed the Calendar Round, which repeated approximately every 52 solar years. The Haabʼ should therefore not be confused with either the Tzolkʼin or the longer historical Long Count.