How many days are there in a leap year?

A leap year has a total of 366 days. This is because, in a regular year, there are 365 days, but in a leap year, an extra day, February 29th, is added to the calendar. This adjustment is necessary to keep the calendar year more closely aligned with the solar year – the time it takes for the Earth to orbit the Sun.

The solar year is approximately 365.2422 days long. If we were to have only 365 days in each year without any adjustments, over time, the calendar would drift out of sync with the natural seasons. This misalignment would lead to events like the solstices (the longest and shortest days of the year) and equinoxes (when day and night are of equal length) shifting around the calendar.

To address this discrepancy, the concept of a leap year was introduced. Here's how it works:

Regular Years (Non-Leap Years): These have 365 days, distributed across 12 months. Each month has its typical number of days: January, March, May, July, August, October, and December have 31 days, while April, June, September, and November have 30 days. February has 28 days.

Leap Years: These have 366 days. As mentioned earlier, the extra day, February 29th, is added to the end of February. This results in a year with 366 days instead of the usual 365.

The rule to determine which years are leap years follows these criteria:

If the year is divisible by 4, it is a leap year.

However, if the year is divisible by 100, it is not a leap year, unless it is also divisible by 400. In that case, it is a leap year.

For example

2000 is a leap year because it's divisible by 400.

1900 is not a leap year because even though it's divisible by 4, it's also divisible by 100 and not by 400.

This adjustment ensures that the average calendar year length (taking into account both regular and leap years) is closer to the solar year length. While it's not a perfect match, this approach helps keep the calendar year reasonably aligned with the natural seasons, making our calendars more accurate for tracking time and scheduling events.