Many different calendars in in use today. They are based on observations ancient people made about the world around them. Some are based on the movement of the Moon around the Earth, some are based on the movement of Earth around the Sun, and some are based on the life cycles of plants and animals.

Nature Based Calendars

The Aboriginal peoples of Australia observe the plants and animals around them as well as weather patterns to give them the correct timing for hunting animals and harvesting plants. For example, when muddy possum prints are found on the ground it is a rainy season after a dry spell. It is a good time to hunt them for food. These calendars vary by location. There are many different languages spoken in Australia.  Different groups of people have their own calendars.

Lunar Calendars

The moon revolves around the Earth. Unlike the sun, the Moon does not create any light. We see it because of the light that is reflected from the sun. It takes 29.53 days for the moon to revolve around Earth. Ancient people would start new months on a particular phase of the moon like a new moon or a crescent. The Islamic calendar is a purely lunar one. Other calendars reconcile with the solar like Asian and Jewish calendars. This is why holidays like Chines New Year and Hanukkah change dates every year.

Moon Phases

To teach kids about the phases of the moon, you can have them eat away at a cookie to learn about the phases. Start with full moon, then waning gibbous, third quarter, and waning crescent. You can rotate them to be waxing crescent, first quarter, waxing gibbous, and full moon.

Waning

Waxing

Why don’t Eclipses happen twice a month?

The orbit of the Moon around the Earth is not in exactly the same plane as the orbit of the Earth around the Sun. The Moon, Earth and Sun are only in a direct line with each other when they are located in the places where the orbits cross each other during full and new moons. Other times of the year the moon is slightly above or below the plane of Earth’s orbit around the Sun when it is a new moon or a full moon.

Solar Calendars

Solar calendars set their year length as the time it takes Earth to revolve around the sun. It is 365 1/4 days (Earth rotations). This is why we must add a leap year day every 4 years. To determine when a year had passed, ancient people looked at what constellations were visible right after sunset and right before sunrise. The new year would begin when those same constellations were in the sky again.

Maya Calendar

The Mayans used a solar calendar and one based on 20 day months. You can find the template for the Calendar and an explanation of how it works here. The Maya numbering system had a dot for the numeral one and a line to represent five. The number seven would be a line with two dots over it.