How many days does it approximately take the Earth to orbit the Sun once?

  • A. Approximately 265 days
  • B. Approximately 300 days
  • C. Approximately 365 days
  • D. Approximately 400 days

💡 Need a hint?

Think about how often we have a leap year and why it is necessary. That extra day in February corrects a small surplus that accumulates every year.

✅ View the answer

The correct answer is C. It takes the Earth approximately 365 days to complete one full orbit around the Sun — but that is not quite the whole story. The orbit actually takes nearly 6 hours longer than those 365 days. Those quarter-days add up over four years to almost a full day, which is why 29 February exists.

📚 More background information

That orbital period — a year — is the foundation of our entire calendar. Without the leap year correction, the calendar would slowly fall out of step with the seasons. A few centuries down the line, and “summer” would fall somewhere in the middle of winter on the calendar.

What many people do not know is that the system has an additional correction built in, because the orbit is just slightly shorter than 365 days and 6 hours. As a result, not every century year is automatically a leap year. A year divisible by 100 only counts as a leap year if it is also divisible by 400. The year 2000 was therefore a leap year, but 1900 was not. That last rule always catches people off guard.

Precisely that kind of “I thought I knew this” knowledge is what makes this a great quiz question. Almost everyone knows the number 365. But why that number is not entirely accurate, and what we do about it, is less straightforward than it might seem.