How do you know what day a holiday falls on? You look at a calendar, of course! But long ago, the only “calendars” people had were the moon, the sun, the stars, and the changing seasons. Even today we still use calendars that follow the changes of the moon and the seasons.

People made the first calendars by dividing a year into 12 “moons,” or months. But they had a problem. A year is the time it takes the earth to travel once around the sun. This comes to about 365 days. A moon-month is the time from one new moon to the next – about 29 1/2 days. There are 12 months in a year. So 12 moon-months come to about 354 days. And this is 11 days less than a year!

Sometimes people added days or months to keep the calendar in step with the seasons. Over the years, some people developed a calendar that matched the seasons. They based this calendar on the solar year, or the time it takes for the earth to circle the sun. It has 365 days.

Picture Credit : Google