In 1559, Sweden moved New Years Day from another date (March 25?) to January 1 on its Julian calendar. The Julian calendar that had January 1 as the New Year Day is known as the Julian-1 calendar.
In 1582, the Gregorian Calendar came into existence as it solved the problem of the calendar running too slow as it eliminated three uses of a February 29th on leap years that are multiples of 100 that are not multiples of 400 (i.e. the years 100, 200, 300, 500, etc., are not leap years, while the years 400, 800, 1200, etc., are leap years.) The Julian Calendar has a leap year day every four years, but since it ran too slow, the Julian Calendar was slow by 11 days during the 16th and 17th centuries.
As more countries adopted the Gregorian Calendar during the first two centuries, some countries remain holdouts and many used one of two versions of the Julian Calendar: the Julian-1, which has New Year's Day on January 1, and the Julian-3-25 or Julian-LD (Lady Day), which has New Year's Day on March 25. Many countries used one of the three calendars named above, but it got confusing as travelers went between countries that didn't use the same calendar. You could travel on November 11 from one country that used the Gregorian Calendar, and arrive in a country on November 6 that used a Julian Calendar a few days later. To be more confused, you could leave a country on February 22, 1703, that used the Gregorian Calendar, and arrive in a country on February 14, 1702 that used a Julian-3-25 Calendar.
The Swedish Empire (which included modern day Finland), stuck with the Julian-1 Calendar almost through the end of the 17th century, but in around 1699 or earlier, the country decided to gradully change from the Julian to the Gregorian Calendar with a plan that went awry.
To ease into the Gregorian Calendar, instead of dropping 11 days, a plan was hatched that would drop all eleven of the upcoming leap year days from 1700 through 1740 until their calendar caught up with the Gregorian Calendar, on March 1, 1740. That was based on a similar fix when Augustus Caesar, who ruled Rome, noticed that the Julian calendar ran too slow by inserting a leap year day every three instead of four years. Augustus solved the problem by eliminating a leap year day from 8 B.C. through 4 A.D., three leap year days in all, and resume the leap year days every four years beginning in 8 A.D. That synched the calendar back in line with the actual Julian calendar. Based on that, the King of the Swedish Empire decided to do the same thing Augustus did 17 centuries ago by skipping the leap year days until their calendar slowed down the pacing of the calendar enough to catch up with the pacing of the Gregorian Calendar.
In 1700, the Swedish Empire skipped February 29 and went directly from February 28 to March 1, but days earlier, the Gregorian Calendar also skipped February 29 as it fell on a year that was a multiple of 100 and was not a multiple of 400. I would call this calendar variation that the Swedish Empire used the Julian-Sweden Calendar. On March 1, 1700, Julian-Sweden date, they were a day fast of the Julian-1 Calendar, which was February 29, 1700, but on the Julian-3-25 Calendar, the date was February 29, 1699, or as some countries preferred to use the dual-dating system, February 29, 1699/1700. It was March 11, 1700 on the Gregorian Calendar on the same date. Now you see how confusing it was getting converting calendar dates between countries that used different calendars?
For reasons unknown, possibly being distracted from the war, the Swedish Empire forgot to skip the years 1704 and 1708, resulting in the two February 29's appearing where they should have been skipped. For 12 years, this confusiuon of differing dates existed until the King of the Swedish Empire decided to retreat in 1712 from the calendar conversion plan.
Insted of dropping ten more days to join the Gregorian Calendar, the country rejoined the Julian-1 Calendar by adding a second leap year day after February 29: February 30. February 29 was the normal leap year day to be inserted every four years, and February 30 represents the leap year day of February 29 in 1700 that was skipped over as part of the calendar synching plan.
So this date, February 30, 1712 Julian-Swedish Date, existed in order for Sweden to realign their ill-fated short-lived calendar without leap year days (no February 29's between 1700 and 1740 inclusive) back to a Julian calendar still in use with some countries. Their attempt to gradually change from the Julian to the Gregorian calendar by dropping leap year days every four years went awry when they forgot to exclude two February 29's in 1704 and 1708 due to a war they were involved in.
February 30, 1712 Julian-Swedish date mapped to February 29, 1712 Julian-1 date, February 29, 1711/2 Julian-Lady Day reckoning date hence the dual dating method until March 24, and March 11, 1712 Gregorian date. For historical purposes, historians running the Today in History almanac news features could make an entry of the event that the Swedish Empire observed a second leap year day, Febuary 30, in 1712, that was used to resync their calendar with the Julian calendar used in many other countries at the time, and observe it on March 11 every year on the Gregorian calendar, or February 29 every four years on the Julian calendar.
The day after, it was March 1, 1712 Julian-1 date, March 1, 1711/2 Julian-Lady-Day date, and March 12, 1712 Gregorian date.
In 1753, Sweden switched to the Gregorian calendar outright by omitting the last 11 days in February (18 through the 28th); the day after February 17, 1753 (Julian) was March 1, 1753 (Gregorian). When Feb 18, 1753 Julian-1 arrived, it was March 1, 1753 Gregorian. Feb 17, 1753 was the last day Sweden used the Julian-1 calendar. England and its colonies also followed suit and joined the Gregorian Calendar in 1752. Some countries countries continued to use a Julian calendar.
So here's all that I found about February 30th, many of which are rumors, hoaxes, misprints, mentions, and even things that sport a "Febuary 30."
In 0045, B.C., it was rumored by the thirteenth-century scholar Johannes de Sacrobosco that the just-reformed Julian calendar, which took effect in 45 B.C., that during leap years, erroneously spaced between three years apart, February had 30 days (while August had 30 during this period), between 45 B.C. and eight B.C. All historical evidence, however refutes Sacrobosco, stating that February during leap years always had 29 days (28 normally) and August always had 31 days.
In 1508, in the book called "The Observatory, Volume 22," a group of paragraphs under the title "the Thirtieth of February" stated that a certain Jane Smyth died on February 30th, 1508.
In 1601, according to the Lord of the Ring series created by J.R.R. Tolkien, a fictional calendar was invented by the Hobbits effective in 1601 that used the Shire Reckoning, beginning with Year 1. This calendar was arranged with 12 months of 30 days each, together with holidays that are assigned to no month. The month the Hobbits call Solmath is rendered in the text as February, but the months in the Shire Calendar begin approximately at the dates when the seasons change and when 1/3 and 2/3 of a season has passed, so the months between the two calendars are off by eight to ten days. The date of February 30, 1 Shire Date using the Gregorian calendar layout, corresponds to the date of Rethe (the third month) 10, 1 Shire Date using the Shire calendar layout, which in turn corresponds to the date of March 2, 1601, on the Gregorian calendar using the Jesus Reckoning. During leap years, February 30 Shire corresponds to March 1 Gregorian.
In 1712, it was possible that somewhere between 100 and 200 babies in Sweden were born on February 30, 1712.
In 1712, it was possible that someone in Sweden died on February 30, 1712.
In 1712, this date, February 30, 1712 Julian-Swedish Date, existed in order for Sweden to realign their ill-fated short-lived calendar without leap year days (no February 29's between 1700 and 1740 inclusive) back to a Julian calendar still in use with some countries. Their attempt to gradually change from the Julian to the Gregorian calendar by dropping leap year days every four years went awry when they forgot to exclude two February 29's in 1704 and 1708 due to a war they were involved in. In 1753, Sweden switched to the Gregorian calendar outright by omitting the last 11 days in February (18 through the 28th); the day after February 17, 1753 (Julian) was March 1, 1753 (Gregorian). February 30, 1712 Julian-Swedish date mapped to February 29, 1712 Julian date, February 29, 1711/12 Julian-Lady Day reckoning date hence the dual dating method until March 24, and March 11, 1712 Gregorian date.
In 1760, a tombstone for Elizabeth H. Cullen stated that she was born on February 30, 1760 and died September 30, 1830.
In 1762, in the book called "The Observatory, Volume 22," it is printed as "(in memory of) William, son of Robert and Ann Myers, who died February 30th, 1762."
In 1847, on the tombstone of Anna B., wife of W. H. Shield, she was born in 1809 and died on February 30, 1847.
In 1851, the date of death of February 31, 1851 is seen on the tombstone of Anna Gladkova, located in the Nikitsky Cemetery in Kursk, Russia.
In 1869, the date of death of February 31, 1869 is seen on the tombstone of Christiana Haag, located in the Old Mission Church Cemetery in Upper Sandusky, Ohio.
In 1930, a rumor of the existence of February 30 dates between the years 1930 through 1940 existed on the Soviet Revolutionary Calendar; but most scholars and proof from the surviving calendars state that the Calendar never used the February 30th date during the lifespan of the Calendar from 1929 - 1940.
In 1931, during the year 1930, the World Calendar was proposed by Elisabeth Achelis with the point of having every January, April, July and October having 31 days and the other eight months having 30, with Worldsday following December 30 and Leapyear Day following June 30. With this World Calendar reform, there would have been a February 30, as well as an April 31, beginning in 1931. The reformed calendar was published from 1931 until 1955; in 1956, she gave up on the reform idea.
In 1951, February 30, 1951, according to a fictional calendar, is the last night of the world in Ray Bradbury's short story, "Last Night of the World."
In 1995, Harpreet Singh of Thakarwal's date of birth was erroneously recorded as being born on February 30, 1995, when he was actually born on February 20th.
In 1997, (Joke Entry), Jay Leno tells a really funny joke involving O. J. Simpson, and the double murder of Nicole Brown Simpson and Ron Goldman.
In 1997, (Joke Entry), “Weird Al” Yankovic released “Macarena” in record stores, but pulled it at the last second.
In 2000, in the year 1999, a rumor swept across the world that the year 2000 was a double leap year, with a February 29th and 30th. The rumor turned out to be a vastly successful hoax.
In 2001, (Joke Entry), The XFL scores a 100 share for NBC on a Saturday night while the movie houses wondered where their audience had gone.
In 2002, (Joke Entry), the French arts institute Canular de Jour Supplementaire honors Kirstie Alley for her much misunderstood opus, “Veronicaʹs Closet.”
In 2002, (Joke Entry) (February 31), Jennifer Lopez marries David Tanny…for a few hours, then is divorced when on their wedding night, she hears David chanting “Oh, Shakira!” Tanny got nothing from the divorce settlement.
In 2003, (Joke Entry) (February 31), Saddam Hussein and Osama bin Laden were named co-winners of the Nobull Piece Prize.
In 2004, (Joke Entry), Britney Spears marries Ben Affleck for zero seconds, a world record!
In 2005, The Symmetry454 Calendar has been running since 2005 though it's unknown if any countries adpoted it. It was created by Dr. Irv Bromberg. Under the system, every month alternates with a four-five-four week-length cycle, with a leap week inserted after December every five or six years. There would have been a February 30, 31, 32, 33, 34 and 35 each year, as well as the same 35 days for May, August and November.
In 2010, according to a post by whitslegit in urbandictionary.com, February 30th is National Gay Pride Day. Since it doesn't exist, the day can be whatever day you want.
In 2011, the Onlies released a song titled "February 30th" sometime in 2011.
In 2012, according to the Weekly World News, February 2012 receives two extra days due to a shift in the earth's axis, creating a new astrological sign, and creating a need to have a February 29 and February 30 on the calendar forever.
In 2012, a restauraunt titled "February 30 Beirut" opened Beirut, Lebanon, during the year 2012.
In 2013, a rumor about Facebook closing for maintenance between February 29, 30 and 31 began making the rounds in 2013.
In 2014, the band, called "The 30th of February," began releasing some albums in 2014 on their bandcamp page.
In 2017, the Hanke–Henry Permanent Calendar was invented in 2011 with the idea of having a leap week occuring every five to six years, with March, June, September and December having 31 days each with the other eight having 30 days for a 364-day calendar, or 371 days with a short seven-day mini-month called Xtra inserted between December and January. There would have been a February 30, as well as a June 31 and September 31 if the calendar was effective in 2017.
In 2017, on February 22, 2017, Stephen Curtis released his e-book titled "February 30th" on Kindle.
In 2020, Thousands of Mennonites across the continent had vowed to go without meat for two whole days on February 30th and 31st of this year.
In 2020, on February 30 and 31, according to justdisney.co, the Walt Disney Company shut down Disney World for two days to give an extended break for their beloved employees.