When was the last leap year?

The most recent leap year was 2020. A leap year, as you may already know, contains an extra day, February 29th, bringing the total number of days to 366 instead of the usual 365. This adjustment helps our calendar align more closely with the Earth's orbit around the Sun.

Leap years are introduced to account for the extra roughly quarter day in the solar year, making up the difference between our standard 365-day calendar and the actual solar year of about 365.2422 days. Without this extra day added every four years, our calendars would gradually drift out of sync with the natural seasons.

Now, let's delve into the specifics and explore the rules that determine leap years:

Dvisibility by 4: Every year that is evenly divisible by 4 is designated as a potential leap year. In the case of 2020, it passes this test, being divisible by 4.

Exception for Centuries: While most years divisible by 4 are leap years, there's an exception for years that are divisible by 100 but not by 400. These years are not leap years. This rule was introduced to fine-tune the calendar system. For instance, while the year 1900 was divisible by 4, it's divisible by 100 without being divisible by 400, so it wasn't a leap year.

Divisibility by 400: This exception means that years divisible by 400 are still leap years. Thus, the year 2000, being divisible by 400, was a leap year.

In the context of the most recent leap year, 2020 met the criteria: divisible by 4, and although it's a century year (divisible by 100), it's also divisible by 400. Therefore, the year 2020 was indeed a leap year, with the extra day added to the end of February.

The inclusion of a leap year in our calendar system demonstrates our efforts to bridge the gap between the man-made calendar and the natural cycles of the Earth's orbit. This periodic adjustment ensures that significant events, such as equinoxes and solstices, continue to occur around the same times each year, maintaining harmony between our calendar and the ever-changing cosmos.