Why Did We Switch to Calendar Years?

Humans have always looked at the sky to tell time. Long ago, people used lunar months, counting the moon's phases. But they noticed that seasons didn't match up perfectly with the moons.

The Romans created a fixed number of days in a year. They added extra days every few years so spring wouldn't turn into winter! This was called the Julian calendar. Later, people found it was still slightly too long by a tiny bit. So they tweaked it again to make our modern calendar.

Now, we use 365 days for most years and add one extra day in leap years every four years. This keeps Christmas in winter and summer vacations in summer! Without these small adjustments, the seasons would slowly wander around like lost pets.