The Aztec calendar was a really special way that the Aztecs kept track of time a long time ago in what is now Mexico.
Imagine you have a super big piece of paper that has a lot of special symbols and pictures on it. This is what the Aztec calendar looked like.
The Aztecs believed that the calendar was given to them by their gods, and it helped them know when to plant crops, when to celebrate special holidays, and when important events would happen.
The calendar had two parts: the first part was a calendar that told the day, month, and year, just like our calendars today. The second part was a special round calendar called a "tonalpohualli" that helped the Aztecs keep track of which days were good for certain activities or were lucky days.
The tonalpohualli was made up of 20 symbols that stood for different days and 13 numbers. The symbols and numbers would rotate together every 260 days, and when they lined up in a certain way, it was a special time for the Aztecs to celebrate.
So, the Aztec calendar was like a big, special paper that helped the Aztecs know what day it was, when important things were happening, and which days were good for certain activities. And it was all made up of really cool symbols and pictures that had meaning for the Aztecs.