365-day calendar 365-day calendar A 365-day calendar consists of exactly 365 days per year (no leap days), and is primarily used in computer models and as an assumption in every-day calculations. For example, a calculation of a daily rate may use an annual total divided by exactly 365. Interest rates in some banks are calculated using a 365-day calendar. Some Mesoamerican calendars used a 365-day year with no leap year, resulting in a gradual shift of the seasons relative to the calendar. This includes the Maya Haab' and the Aztec Xiuhpohualli calendars. Some versions of the Zoroastrian calendar also use a fixed
Mesoamerican calendars calendar, a ritual calendar with no confirmed correlation to astronomical or agricultural cycles. Apparently the earliest Mesoamerican calendar to be developed, it was known by a variety of local terms, and its named components and the glyphs used to depict them were similarly culture-specific. However, it is clear that this calendar functioned in essentially the same way across cultures, and down through the chronological periods it was maintained. The second of the major calendars was one representing a 365-day period approximating the tropical year, known sometimes as the "vague year". Because it was an approximation, over time the seasons and