2020 was a leap year, a 366-day-long year.
Every four years, we add an extra day, February 29, to our calendars. These extra days – called leap days which help synchronize our human-created calendars with Earth’s orbit around the sun and the actual passing of the seasons.
Why do we need them? Blame Earth’s orbit around the sun, which takes approximately 365.25 days.
It’s that .25 that creates the need for a leap year every four years.