5 Dates You Won't Find on Your Calendar

ThinkStock/Erin McCarthy
ThinkStock/Erin McCarthy

While you may be a bit fuzzy on which months have 30 days and which have 31, it’s safe to say you’re pretty familiar with the months and days of the year. But due to unusual record-keeping practices or because of months that were eliminated over the centuries, there are a few days you’ll never see on your joke-a-day calendar.


At midnight every New Year’s Eve, we go from December 31 to January 1. Simple, right? That’s how it works for everyone ... except astronomers. Each year, astronomers keep track of the movements of various planets and stars, which are compiled into what’s called an ephemeris. While it’s useful for things like space travel and positioning telescopes, GPS systems also use the data to properly function.

The thing about ephemerides (the plural of ephemeris) is that they don’t reference any year other than the one for which they were written. So if you had an ephemeris for the year 2000, you wouldn’t find any mention of 1999 or 2001. Generally speaking, it shouldn’t be necessary, though, since it’s only for that particular year anyway.

Except when you referenced January 1, that is. Because some more detailed ephemerides will list the previous day’s celestial positions for reference purposes, the ephemeris would have to have information for December 31. But, since the ephemeris doesn’t refer to any other year, this date will instead often be called January 0. Going back to our year 2000 example, an ephemeris for that year might list Prince’s favorite day, December 31, 1999, as January 0, 2000 instead.

It’s worth noting that many modern day ephemerides have dropped the use of January 0 entirely, but there are others that still use it.

And back in the 1920s, several groups lobbied for a calendar with 13 months, each with four weeks. To reach 365 days, their plan was to add "January 0."


You may have a friend or relative in your life whose birthday is February 29. Maybe they fudge it and celebrate on February 28 or March 1 every year, or possibly they just have a mega-party every four years. (Or they have a mega-party every year, because why not.) So imagine how frustrating it’d be to have been born in the Swedish Empire on February 30, 1712, the only day of its kind in history.

Naturally, it was a pretty complex set of events that led to February 1712 getting two leap days. Our modern, Western calendar is called the Gregorian calendar, which was developed under Pope Gregory XIII. It’s basically just a series of improvements to the Julian calendar, created by Julius Caesar.

While the Gregorian calendar was completed in 1582, adoption by many countries was slow, so it took over 100 years for the Swedish Empire (which was primarily Protestant and not Catholic) to adopt it. Because the Julian to Gregorian swap included a difference of ten days, many regions simply skipped their calendar ahead a week and a half. The Swedish Empire decided to roll out the difference more gradually, and intended to skip leap days for forty years, starting in 1700, until the calendar was finally correct.

Except that didn’t happen because, shortly afterward, war broke out and everyone forgot about the leap days until 1712, when Sweden’s King, Charles (or Karl) XII, declared that they would forget about the Gregorian calendar and just switch back to the Julian instead. Since they did manage to skip one leap day, in 1700 (which was a leap year under the Julian calendar, but not the Gregorian), they simply decided to add it back onto the calendar that February—meaning that February 1712 had two leap days according to Sweden’s calendar, which gave them the only February 30 in history. (Sweden finally went through with the Gregorian switch in 1753 and just skipped ahead a few days, like everyone else.)

3. MARCH 0

While you could think of February 30 as some weird kind of March 0, they’re not the same thing (though they do both involve leap years). If someone asked you what the day before March 1 is, you’d probably ask them, “What year?” March 0 is, like January 0, simply a reference to the day before it, but it’s useful since March 0 can be either February 28 or 29, depending on the year.

While this is occasionally used in software (some old versions of Microsoft Excel will accept 3/0 as a date and simply plug in the correct day for the particular year, for example), it’s more commonly found in something known as the Doomsday rule.

It sounds fairly ominous, but the Doomsday rule is just a method for calculating what day of the year falls on for any given date. For example, by following the Doomsday rule, you could quickly tell that January 19, 1481 was a Wednesday. How? By figuring out what creator John Conway calls “the Doomsday.” This is the day of the week that certain calendar days will always fall on in a given year. April 4, June 6, and August 8 are just a few days of the year that will always fall on that year’s Doomsday. Another big one? March 0, i.e., the final day of February.

So, using 1481 as our example again, you can use a formula to determine that its Doomsday was Monday. (For the record, 2013’s Doomsday is Thursday.) From there, we could quickly ascertain that March 0 was a Monday, and for that particular year, February only had 28 days (since it was not a leap year), making “March 0” Monday, February 28, 1481. If you’re mathematically-minded, it’s a fun challenge. If you’re not, well, you can always look the day up on the internet or use a Doomsday calculator.


There aren’t just odd and unusual days of the year. There are entire months as well. Remember the episode of The Simpsons where the school ordered faulty calendars with a 13th month (called Smarch)? Well, as it happens, we kind of had that once upon a time—namely, those left over from the days of the Roman calendar, which preceded the aforementioned Julian calendar. Much like how the process of moving from the Julian calendar to the Gregorian calendar left a few odd days out, the move from the Roman calendar to the Julian one actually added some.

These days, 67 in all, were then added into a pair of months between the November and December of 45 BC, and were referred to as intercalaris prior and intercalaris posterior, which are often called Undecimber (pronounced like “oon,” not “uhn”) and Duodecimber in modern days.

These names refer to the fact that December is named after the Latin word for ten (which itself came from the fact that the Roman calendar originally only had ten months and not twelve), while the Latin words for eleven and twelve (or in this case, thirteen and fourteen) are undecim and duodecim.

What’s more, the terms have even come to be used in modern computing. The Java programming language includes support for a 13-month calendar, and it refers to the 13th month as Undecimber.


Speaking of the Roman calendar, by the time Julius Caesar came along, it hadn’t had ten months for quite a while. Nearly 600 years, in fact. The Roman calendar that Caesar reformed was itself a reformed calendar constructed by King (not Emperor) Numa Pompilius sometime in the 7th century BC.

Prior to Pompilius’ changes, the Roman calendar, as we mentioned, had ten months: Martius, Aprilis, Maius, Iunius, Quintilis, Sextilis, September, October, November, and December. (Quintilis was later renamed Julius after Julius Caesar himself, while Sextilis was changed to Augustus in honor of his son/grand-nephew, Caesar Augustus.) King Numa Pompilius added Januarius and Februarius, giving us the twelve months we have today … except he also added another, forgotten month that hasn’t been in use for millennia: Mercedonius.

Mercedonius was a kind of a leap month, situated between Februarius and Martius, and was approximately 27 days. Although there was apparently some kind of formula to determine in which years Mercedonius was used and in which years it wasn’t, the implementation was spotty, since it was up to whoever the current Pontifex Maximus was at the time to decide if the month was used or not.

Since the month was used so sloppily, Julius Caesar simply eliminated it entirely when constructing the Julian calendar, rearranged the days throughout the year, and made a simple, easy-to-follow leap day system.

11 Memorable Facts About Cats the Musical

Mike Clarke/Getty Images
Mike Clarke/Getty Images

“It was better than Cats!” Decades after Andrew Lloyd Webber's famed musical opened on Broadway on October 7, 1982, this tongue-in-cheek idiom remains a part of our lexicon (thanks to Saturday Night Live). Although the feline extravaganza divided the critics, it won over audiences of all ages and became an industry juggernaut—one that single-handedly generated more than $3 billion for New York City's economy—and that was before it made a return to the Great White Way in 2016. In honor of Andrew Lloyd Webber's birthday on March 22, let’s take a trip down memory lane.

1. The work that Cats the musical is based on was originally going to include dogs.

Old Possum’s Book of Practical Cats, published in 1939, is a collection of feline-themed poems written by the great T. S. Eliot. A whimsical, lighthearted effort, the volume has been delighting cat fanciers for generations—and it could have become just as big of a hit with dog lovers, too. At first, Eliot envisioned the book as an assemblage of canine- and tabby-related poems. However, he came to believe that “dogs don’t seem to lend themselves to verse quite so well, collectively, as cats.” (Spoken like a true ailurophile.) According to his publisher, Eliot decided that “it would be improper to wrap [felines] up with dogs” and barely even mentioned them in the finished product.

For his part, Andrew Lloyd Webber has described his attitude towards cats as “quite neutral.” Still, the composer felt that Eliot’s rhymes could form the basis of a daring, West End-worthy soundtrack. It seemed like an irresistible challenge. “I wanted to set that exciting verse to music,” he explained. “When I [had] written with lyricists in the past … the lyrics have been written to the music. So I was intrigued to see whether I could write a complete piece the other way ‘round.”

2. "Memory" was inspired by a poem that T.S. Eliot never finished.

In 1980, Webber approached T.S. Eliot’s widow, Valerie, to ask for her blessing on the project. She not only said “yes,” but provided the songwriter with some helpful notes and letters that her husband had written about Old Possum’s Book of Practical Cats—including a half-finished, eight-line poem called “Grizabella, the Glamour Cat.” Feeling that it was too melancholy for children, Eliot decided to omit the piece from Practical Cats. But the dramatic power of the poem made it irresistible for Webber and Trevor Nunn, the show’s original director. By combining lines from “Grizabella, the Glamour Cat” with those of another Eliot poem, “Rhapsody on a Windy Night,” they laid the foundation for what became the powerful ballad “Memory.” A smash hit within a smash hit, this showstopper has been covered by such icons as Barbra Streisand and Barry Manilow.

3. Dame Judi Dench left the cast of Cats when her Achilles tendon snapped.

One of Britain’s most esteemed actresses, Dench was brought in to play Grizabella for Cats’s original run on the West End. Then, about three weeks into rehearsals, she was going through a scene with co-star Wayne Sleep (Mr. Mistoffelees) when disaster struck. “She went, ‘You kicked me!’” Sleep recalls in the above video. “And I said, ‘I didn’t, actually, are you alright?’” She wasn’t. Somehow, Dench had managed to tear her Achilles tendon. As a last-minute replacement, Elaine Paige of Evita fame was brought aboard. In an eerie coincidence, Paige had heard a recorded version of “Memory” on a local radio station less than 24 hours before she was asked to play Grizabella. Also, an actual black cat had crossed her path that day. Spooky.

4. To finance the show, Andrew Lloyd Webber ended up mortgaging his house.

Although Andrew Lloyd Webber had previously won great acclaim as one of the creative minds behind Jesus Christ Superstar and other hit shows, Cats had a hard time finding investors. According to choreographer Gillian Lynne, “[it] was very, very difficult to finance because everyone said ‘A show about cats? You must be raving mad.’” In fact, the musical fell so far short of its fundraising goals that Webber ended up taking out a second mortgage on his home to help get Cats the musical off the ground.

5. When Cats the musical came to Broadway, its venue got a huge makeover.

Cats made its West End debut on May 11, 1981. Seventeen months later, a Broadway production of the musical launched what was to become an 18-year run at the Winter Garden Theatre. But before the show could open, some major adjustments had to be made to the venue. Cats came with an enormous, sprawling set which was far too large for the theatre’s available performing space. To make some more room, the stage had to be expanded. Consequently, several rows of orchestra seats were removed, along with the Winter Garden’s proscenium arch. And that was just the beginning. For Grizabella’s climactic ascent into the Heaviside Layer on a giant, levitating tire, the crew installed a hydraulic lift in the orchestra pit and carved a massive hole through the auditorium ceiling. Finally, the theater’s walls were painted black to set the proper mood. After Cats closed in 2000, the original look of the Winter Garden was painstakingly restored—at a cost of $8 million.

6. Cats the musical set longevity records on both sides of the Atlantic.

The original London production took its final bow on May 11, 2002, exactly 21 years after the show had opened—which, at the time, made Cats the longest-running musical in the West End’s history. (It would lose that title to Les Miserables in 2006.) Across the pond, the show was performed at the Winter Garden for the 6138th time on June 19, 1997, putting Cats ahead of A Chorus Line as the longest-running show on Broadway. To celebrate, a massive outdoor celebration was held between 50th and 51st streets, complete with a laser light show and an exclusive after-party for Cats alums.

7. One theatergoer sued the show for $6 million.

Like Hair, Cats involves a lot of performer-audience interaction. See it live, and you might just spot a leotard-clad actor licking himself near your seat before the curtain goes up. In some productions, the character Rum Tum Tugger even rushes out into the crowd and finds an unsuspecting patron to dance with. At a Broadway performance on January 30, 1996, Tugger was played by stage veteran David Hibbard. That night, he singled out one Evelyn Amato as his would-be dance partner. Mildly put, she did not appreciate his antics. Alleging that Hibbard had gyrated his pelvis in her face, Amato sued the musical and its creative team for $6 million.

8. Thanks to Cats the musical, T.S. Eliot received a posthumous Tony.

Because most of the songs in Cats are almost verbatim recitations of Eliot’s poems, he’s regarded as its primary lyricist—even though he died in 1965, long before the show was conceived. Still, Eliot’s contributions earned him a 1983 Tony for Best Book of a Musical. A visibly moved Valerie Eliot took the stage to accept this prize on her late spouse’s behalf. “Tonight’s honor would have given my husband particular pleasure because he loved the theatre,” she told the crowd. Eliot also shared the Best Original Score Tony with Andrew Lloyd Webber.

9. The original Broadway production used more than 3000 pounds of yak hair.

Major productions of Cats use meticulously crafted yak hair wigs, which currently cost around $2300 apiece and can take 40 hours or more to produce. Adding to the expense is the fact that costumers can’t just recycle an old wig after some performer gets recast. “Each wig is made specifically for the actor,” explains wigmaker Hannah McGregor in the above video. Since people tend to have differently shaped heads, precise measurements are taken of every cast member’s skull before he or she is fitted with a new head of hair. “[Their wigs] have to fit them perfectly,” McGregor adds, “because of the amount of jumping and skipping they do as cats.” Perhaps it should come as no surprise that, over its 18-year run, the first Broadway production used 3247 pounds of yak hair. (In comparison, the heaviest actual yaks only weigh around 2200 pounds.)

10. A recent revival included hip hop.

In December 2014, Cats returned to the West End with an all-new cast and music. “The Rum Tum Tugger,” a popular Act I song, was reimagined as a hip hop number. “I’ve come to the conclusion, having read [Old Possum’s Book of Practical Cats] again, that maybe Eliot was the inventor of rap,” Webber told the press.

11. Another revival featured an internet-famous feline for one night only.

On September 30, Grumpy Cat made her Broadway debut in Cats, briefly taking the stage with the cast. Despite being named Honorary Jellicle Cat, she hated every minute of it.

11 Words That Started Out As Spelling Mistakes

A woman sneezing, which in Middle English would have been called a fneze instead.
A woman sneezing, which in Middle English would have been called a fneze instead.

The word irregardless might not be to everyone’s taste, but there’s no denying that if you were to use it in a sentence, you’d be perfectly understood—and that’s more than enough evidence for it to have been accepted into many dictionaries (albeit flagged as non-standard or informal), including Oxford Dictionaries, Merriam-Webster, and even the hallowed Oxford English Dictionary, which has so far been able to trace it back as far as 1912. So despite it having its origins in an error, and irregardless of what you might think of it, there’s no denying irregardless is indeed a word—and it’s by no means alone.

1. Expediate

Meaning “to hasten” or “to complete something promptly,” the verb expediate is thought to have been invented by accident in the early 1600s when the adjective form of expedite, meaning “ready for action” or “alert,” was misspelled in an essay by the English politician Sir Edwin Sandys (it was later corrected).

2. Culprit

There are several different accounts of the origin of culprit, but all of them seem to agree that the word was born out of a mistake. Back when French was still the language of the law in England in the Middle Ages (a hangover from the days of the Norman Conquest), the phrase Culpable, prest d’averrer nostre bille—literally “guilty, ready to prove our case”—was apparently the stock reply given by the Clerk of the Crown whenever a defendant gave a plea of not guilty. In the court records, this fairly long-winded phrase was often abbreviated just to cul. prit., and, as the Oxford English Dictionary explains, “by a fortuitous or ignorant running together of the two,” the word culprit was born.

3. Despatch

Despatch is a chiefly British English variant of dispatch, often used only in formal contexts like the name of the political despatch box in the House of Commons. The e spelling apparently began as a phonetic variation of the original I spelling, but after Samuel Johnson included it in his Dictionary of the English Language in 1755, its use was legitimized and thrived in the 19th century. Because Johnson himself preferred the I spelling in his own writings, however, it's supposed that he included the e spelling by mistake and inadvertently popularized the error.

4. Nickname

Nicknames were originally called eke names, with the verb eke used here in the sense of “to make longer” or “to provide an addition.” Sometime in the 13th century, however, “an eke-name” was mistakenly interpreted as “a neke-name,” and the N permanently jumped across from the indefinite article an to the verb eke. The same error—known linguistically as “rebracketing” or “junctural metanalysis”—is responsible for nadders, numpires, and naprons all losing their initial Ns in the Middle English period.

5. Ammunition

Ammunition derives from a faulty division of the French la munition, which was incorrectly misheard as l'amonition by French soldiers in the Middle Ages, and it was this mistaken form that was borrowed into English in the 1600s.

6. Scandinavia

Scandinavia was originally called Scadinavia, without the first N, and is thought to take its name from an island, perhaps now part of the Swedish mainland, called Scadia. According to the Oxford English Dictionary, the extra N was added in error by the Roman scholar Pliny the Elder, and has remained in place ever since.

7. Syllabus

If all had gone to plan in the history of the word syllabus, those two Ls should really be Ts: Syllabus was coined as a Latin misreading of an Ancient Greek word, sittybos, meaning “a table of contents.”

8. Sneeze

Oddly, sneeze was spelled with an F and not an S, fneze, in Middle English, which gives weight to the theory that it was probably originally coined onomatopoeically. At least one explanation of why the letter changed suggests that this F inadvertently became an S sometime in the 15th century due to continual misreadings of the long lowercase f as the old-fashioned long S character, ſ.

9. Ptarmigan

The ptarmigan is a bird of the grouse family, found in mountainous and high-latitude environments. Its bizarre name with its initial silent P is something of a mystery, as the original Scots word from which it derives, tarmachan, shows no evidence of it and there’s little reason why one should ever have to have been added to it—except, of course, if it were a mistake. The P spelling first emerged in the late 1600s, and is thought to have been a mistaken or misguided attempt to ally the name to the Greek word for a wing, pteron, and eventually this unusual P spelling replaced the original one.

10. Sherry

Sherry takes its name from the southern Spanish port of Xeres (now Jerez de la Frontera in Cádiz) and was originally known as vino de Xeres, or “wine of Xeres.” This name then morphed into sherris when sherry first began to be talked about in English in the early 17th century, but because of that final S, it didn’t take long for that to be misinterpreted as a plural. Ultimately, a mistaken singular form, sherry, emerged entirely by mistake in the early 1600s.

11. Pea

Another word that developed from a plural-that-actually-wasn’t is pea. One pea was known as a pease in Middle English, but because of that final “s” sound, pease was quickly misinterpreted as a plural, giving rise to a misguided singular form, pea, in the 17th century. The actual plural of pease in Middle English, incidentally, was pesen.

This list first ran in 2016.