While the Julian calendar came to the region when it was conqured by Spain in the 16th century, and the Gregorian calendar is now in general use, in a few communities some Native Americans of the area still use the ancient count of days as well.
All of the Mesoamerican cultures shared a 260 day ritual calendar, for example, the Tzolkin of the Maya civilization. In many Mesoarmeican cultures people were given the name of the day in this cycle on which they were born (sometimes in addition to another name).
This 260 day cycle ran concurrently with the solar year. These two calendars came together every 52 years.
This 52 year cycle, sometimes called a Calendar round, was very significant. Commonly elaborate rituals would be held at the end of each calendar round, with all fires extinguished, old pots broken, and a new fire kindled symbolizing a fresh start.
There was a belief in cycles within time, for example that if a significant event happened on a certain day in the 52 year cycle, a similar or related event was likely to happen on the same day in the next 52 year cycle.
This 52 year cycle was by far the most important for most Mesoamericans, with the apparent exception of the elite Maya elite until the end of the Classic Era, who gave equal importance to the Maya Long Count Calendar.