We all know that there are 365 days in a year, plus an extra day every fourth year, or leap year. These numbers are the result of years of study of the sun and the seasons. The Maya, working without scientific tools, calculated that there were 365.2420 days in a year. Modern astronomers used modern technology to measure the year at 365.2422 days!

The Maya created a solar calendar, or calendar based on the movement of the sun. This calendar is similar to our calendar, but there are some differences. We divide our year into twelve months. The Maya divided their year into eighteen months with names like Pop and Zip. A special five-day “month” completed the 365-day year.

Besides their 365-day solar calendar, Maya astronomers created another calendar called the Sacred Round. This calendar was 260 days long and was used to keep track of religious holidays and other important events.

Because the Maya had two calendars, each day had two names. One name came from the Sacred Round and the other from the solar calendar. This also meant that all Maya people had two birthdays.