1. Calendars help us track time using the Sun and Moon! Ancient humans realized that tracking the sun and moon could help them know when seasons would change. A calendar is simply a system or chart used to organize days, weeks, and months throughout the year.

2. The word "calendar" comes from ancient Rome. In ancient Rome, the first day of every month was called the calends, which was when people had to pay off their debts. Romans kept track of these tax days on ledger sheets called calendarium!

3. Leap years give us an extra day in February. It actually takes Earth about 365 days and 6 hours to orbit all the way around the Sun. To make sure our calendar doesn't get out of sync with the seasons, those extra 6 hours add up every four years to create February 29th!

4. Months are named after Roman gods and numbers. Many month names have cool historical meanings! July was named after Julius Caesar, August after Emperor Augustus, and September through December come from old Latin numbers (like septem meaning seven).

5. The ancient Maya invented a super complex calendar. The Maya civilization created multiple calendars, including a sacred 260-day ritual calendar and a 365-day solar calendar. Their rotating stone calendars tracked cosmic cycles with incredible accuracy.

6. There are different types of calendars all over the world. While most of the world uses the Gregorian calendar, many cultures use other systems! For example, the Islamic calendar is based on the phases of the Moon, and the Chinese calendar combines both the Sun and Moon.

7. Pocket planners used to be carried everywhere. Before smartphones, people carried small paper datebooks or wall calendars everywhere to remember birthdays, school holidays, dentist appointments, and soccer practice.