Today is Feb. 29, an extra special day that only happens every four years, save for a few notable exceptions. This phenomenon is known as a leap year and actually serves a crucial purpose for global timekeeping.

According to NASA, a full orbit around the sun takes 365 days, six hours and nine minutes. In the U.S., we follow the Gregorian calendar, a solar calendar that takes these few extra hours into account, giving us leap years.

The Gregorian calendar is actually a modified version of the Republican calendar. That calendar, established in Ancient Rome around 500 BC, was made up of 12 months based on lunar cycles. This meant that years were only 355 days, approximately 10 days short of a full orbit around the sun.

In an effort to correct this time differential, the Republican calendar featured an extra month called Mercedonius every two to three years. The issue was that the higher-ups in the Roman Empire were allowed to change the calendar and often did so to extend their reign of power. With all its consistencies, the general population found the calendar too confusing.

In true Julius Caesar fashion, the emperor created the aptly-named Julian calendar in 45 BC, giving us the standard 365-day year. The Julian calendar also introduced the world to the 366-day leap year, occurring every four years. It was the closest calendar yet to an actual orbit around the sun, but an estimated 11-minute annual time difference created discrepancies over time.

Notably, the Catholic church had a hard time determining when Easter was to be celebrated each year, as by that time, a nearly 10-day shift had accumulated since Caesar’s reign. Easter is traditionally held after the Spring equinox on the first Sunday after a full moon.

As a result, Pope Gregory XIII created the Gregorian calendar in 1582, setting in place our modern, albeit more complicated, leap year rules.

Under the Gregorian calendar’s rules, leap years occur every four years – unless that year is divisible by 100 and not by 400. This means that certain turn-of-the-century years, such as the year 2000, are leap years, but others, including 1900 and 1800, are not.

The last time the world saw a leap year was four years ago on Feb. 29, 2020. It goes without saying that 2020 was a pivotal year for both the U.S. and the world as a whole.

On this day four years ago, the U.S. saw its first death in the COVID-19 pandemic — a man in his 50s who died at the Kirkland Life Care Center in Kirkland, Wash. At the time, the virus was still referred to as “coronavirus” or “corona” by the general public, and tests for the virus were only available for those who had traveled to Wuhan, China. The man had not recently traveled, and as a result, his death sparked fear that the virus was spreading domestically.

That panic manifested in the American economy as well. That week, the Dow Jones Industrial Average fell 12 percent, the fastest drop since the Great Recession of 2008. The NASDAQ also fell 10.5 percent, falling just a few points short of an all-time worst drop.

In geopolitical news, the U.S. signed a landmark agreement with the Taliban in hopes of ending the nearly 20-year war in Afghanistan. Signed in Doha, Qatar, the agreement created an official timeline of 14 months for the removal of all U.S. and NATO troops and a resolution for a “permanent and comprehensive” ceasefire.

Back in the U.S., Joe Biden won the South Carolina Democratic Presidential Primary on Feb. 29, 2020 with a vote of 48.6 percent, beating Sen. Bernie Sanders and businessman Tom Steyer. Biden’s victory in South Carolina paved the way for his eventual win in the general election in November 2020.

In popular culture, the number one hit song on the Billboard Hot 100 chart was “The Box” by Roddy Ricch, followed by “Life is Good” by Future ft. Drake and “Circles” by Post Malone. At the box office, the top movies were “The Invisible Man,” “Sonic the Hedgehog” and “The Call of the Wild.”

It’s remarkable to see how much the world has changed since the last February 29. As we look ahead to the future, who knows where we’ll be on the next leap year. Here’s to 2028!

Nathan Legare can be reached at [email protected].