Think Feb. 29, leap year and leap day are rare? Feb. 30 was a real date in history. Twice

The rare date Feb. 29 is coming up − and though it only crops up every four years, it is indeed real.

But what about Feb. 30 or March 32?

Sorry, folks. Those are not. An online search for "March 32nd" will bring up April Fool's Day results. However, Feb. 30 was used twice in history. And never again.

In honor of Leap Day 2024 and the Leap Year hoopla for Feb. 29 − a date not seen since Feb. 29, 2020 − we've tackled the even more rare date and little-known tale of Feb. 30.

When is Leap Day 2024?

Leap Day is Thursday, Feb. 29, 2024.

After 2024, when is the next Leap Day?

After this year, the next leap year and leap day is Feb. 29, 2028.

Leap year: Why we need leap day and other surprising facts about Feb. 29

Why does Leap Day occur once every four years?

Our calendar is not entirely in sync with our planet's trip around the sun.

A common year has 365 days on the calendar while a leap year boasts that extra day. Their purpose keeps our calendar in sync with the seasons and solar year, or the length of time it takes the earth to complete its orbit around the sun, which is about 365¼ days, according to timeanddate.com.

Every four years, we have 366 days on the calendar. If we didn't observe leap years, our seasons would be messed up as our equinoxes and summer and winter solstice would no longer align with the seasons.

"If there were no leap years, the seasons would completely swap every 750 years, i.e. the middle of summer would become the middle of winter − calendar climate change," astronomy expert Dr. Stephen Hughes of Queensland University of Technology said in a Feb. 29, 2012 (a Leap Year) article on AsianScientist.com.

If your birthday is on Feb. 29, which day do you use to celebrate? What date do you use for official documents or ID?

Those born on that day don't always get to celebrate their actual birthday — since that date occurs only every four years. Someone born on Leap Day typically celebrates birthdays on Feb. 28 or March 1. But Feb. 29 is still used for identification and important documents.

Is there a February 30? Can there be 2 Leap Days in one year?

According to timeanddate.com, in 1700, Sweden leaders had planned to convert from the Julian calendar to the Gregorian calendar. Like the Gregorian calendar, the Julian calendar has 12 months and 365 days "with each fourth year having 366 days and the months each having 31 or 30 days except for February which has 28 or in leap years 29 days," Merriam-Webster Dictionary's site explains.

A year is a leap year if it is evenly divisible by 4. If the year can be evenly divided by 100, it is not a leap year unless the year is also evenly divisible by 400, according to mathisfun.com. For example, 2000 and 2400 are leap years, but 1800, 1900, 2100, 2200, 2300 and 2500 are not.

Because 1700 is divisible by 4, it was a leap year (in the Gregorian calendar and Julian calendar). However, the timeanddate.com post says, "1704 and 1708 became leap years by error. This left Sweden out of synchronization with both the Julian and the Gregorian calendars, so the country reverted back to the Julian calendar."

The confusion grew: "February 30, 1712, came into existence in Sweden when the Julian calendar was restored and two leap days were added that year." Sweden’s final conversion to the Gregorian calendar occurred in 1753. But the country had to do something drastic with its calendar to catch up: An 11-day correction was applied that year, and, after Feb. 17, the next day was March 1, according to timeanddate.com.

While Sweden added Feb. 30 to its 1712 calendar in error, the former Soviet Union observed Feb. 30 in 1930 and 1931. According to History, the Soviet government didn't see Sundays as a day of rest from six days of labor, but as a threat to progress. Enter the "Soviet calendar," which had five-day continuous work weeks and 30-day months. Workers got a random day off during the 5-day week and the remaining days of the year were made national holidays. After 1931, several adjustments were made to the calendar but it was eventually abandoned in 1940.

Feb. 30 anniversary?

What was there to do on Feb. 30, 1712? For Swedes Sven Hall and Ellna Jeppsdotter the answer was to get married.

The couple wed in Ystad, Sweden on Feb. 30 but sadly were never able to celebrate an anniversary on their wedding date, WSJ reported.

This article originally appeared on Florida Today: When is leap year? What day is February 29? Do calendars have March 32