What is a Leap Year?

TL;DR

Leap years are needed to keep our calendar in sync with the seasons because a year is longer than our calendar predicts.

Transcript

A calendar year is made of three hundred and sixty five days -- a number that refuses to be divide nicely, which is why we end up with uneven months of either 30 or 31 days. Except for February -- the runt of the litter -- which only gets 28... except when it gets 29 and then the year is 366 days long. Why does that happen? What kind of crazy unive... Read More

Key Insights

• 😎 The length of a year is connected to Earth's orbit around the sun and the cycle of seasons.
• 🥳 The day/night cycle used for counting days is not directly related to the yearly cycle.
• 🥳 Leap years, with an extra day added to February, help keep the calendar in alignment with the seasons.
• 🛩️ Even with leap years, there is still a small error in the calendar, which is corrected by skipping leap years during certain centuries.
• 🥳 The variability in the length of a day makes it impossible to create a perfect calendar without adjustments.
• 🥳 The current calendar system has an error of just one day over almost eight thousand years.
• 📅 Leap years and calendar adjustments will keep the calendar in sync with the seasons for the next eight millennia.

Questions & Answers

Q: Why are some years longer than others?

Some years have an extra day, known as a leap year, to correct the misalignment between the calendar and the seasons caused by the day/night cycle not being connected to the yearly cycle.

Q: How often do leap years occur?

Leap years occur every four years, except for years divisible by 100 but not by 400. This prevents an overcorrection and keeps the calendar in better alignment with the seasons.

Q: What happens if leap years are not used?

Without leap years, the calendar would slowly fall out of sync with the seasons, leading to holidays and seasons occurring at different times of the year.

Q: Is there a perfect calendar that can accurately track the year?

Due to the variability in the length of a day and the gradual decrease in its length, it is impossible to create a perfect calendar that will last forever without needing adjustments.

Summary & Key Takeaways

• A year is the time it takes for Earth to orbit the sun and is connected to the cycle of seasons.

• The day/night cycle, which is used to count days, is not connected to the yearly cycle, causing a misalignment between the calendar and the seasons.

• Leap years, where February gets an extra day, help to correct this misalignment, but a small error still remains.