know the Maya had two calendars? One was tied to the astronomical year,
and had 365 days like ours. The other was shorter,
260 days, and was associated with rituals.
of El Castillo in Chichén Itzá was built to reflect the
Mayan astronomical year. Each side has 91 steps with a final step at
the top, so there are 365 steps total. The Pyramid was constructed so
that it marks the equinoxes—the two days of the year when there
are equal amounts of day and night. On these days, the sun casts an
image of a snake that appears to move down the pyramid. You can see
it happen by watching our webcast from Chichén
of time were central to Mayan life, so the times when the two calendars
came together were considered special events. This activity will help
you understand how the Maya figured out when those coinciding days would
Grade 6 and above
National Standards Addressed
History and Nature of Science: History of Science
History and Nature of Science: Historical Perspectives
• Principles and Standards for School Mathematics
Numbers and Operations
Gear ratios, smallest common multiple, prime factors, prime numbers
"How Gear Ratios Work"
from How Stuff Works
and information about the Mayan calendar
From Web Exhibits, by the Institute for Dynamic Education Advancement
• One event that happens for you annually is your birthday. What
if you were born on February 29? That "leap day" occurs only
once every four years. How often could you celebrate your real birthday?
How "old" would you be now if you counted only that date as
your birthday? How "old" would the oldest person in your family
• What role do cycles of time play for us in the modern world?
Often students have defined schedules at school and after school, and
parents have regular schedules as well. Can you think of a time in your
life when you've had to look through two different schedules to find
coinciding dates? How did you do it?
Most calendars have been developed in relation to astronomical events
and the change of seasons. What events do you think our current calendar
is based on? What things in the sky change, and how long do they take
to go through their cycles?
Many cultures have their own calendars. What other number systems have
been used for calendars? Do you know any holidays or events that follow
a different calendar than the one you usually use? You can read about
different calendars on the Web Exhibits Web site: