Wednesday marks the last day of February, the shortest month in the Gregorian calendar. It doesn’t have to be this way, according to some advocates who propose a calendar where every year is 13 months and every month is 28 days. It sounds like a drastic change to a calendar that’s been in use since 1582, but dig a little deeper and the idea makes a lot of sense.

The idea is simple. Each month has four, seven-day weeks, making a total of 28 days. There are 13 months in a year, totaling 364 days, with a new month in between June and July called “Sol” to mark the summer solstice. The leftover day is a special Year Day, with two such days every four years.

The idea was first proposed by British railway worker Moses B. Cotsworth, who devised it in 1902 as a way of making his job easier. George Eastman, head of Kodak, used the calendar in his company from 1924 to 1989, but employees didn’t live their lives by the strange structure and stuck to Gregorian outside of work. A proposal put forth to the League of Nations attracted a great deal of interest, but that too fell by the wayside as World War II disbanded the league.

The design has a number of advantages. It means the 8th is always a Sunday no matter the month, and the same applies to every other day. Holidays like Thanksgiving wouldn’t move around the calendar anymore. Monthly and quarterly data becomes easier to compare, with both measurements an equal number of days. It also means never checking when the month ends.

The idea has since occasionally come up in fiction. The Simpsons lampooned the idea during a Treehouse of Horror Halloween special, where a particularly spooky segment takes place on the 13th day of the 13th month. Marge explains that the school calendars were misprinted, and Homer can be heard complaining about the “lousy Smarch weather.”

The Simpsons episode actually raises one of the downsides of the calendar. It would mean having a 13th month every year, and also means every month would contain a Friday the 13th. It may sound like a small detail to some, but don’t forget that Microsoft never released a version 13 of Office, and data from 2015 showed 574 Manhattan condos lack a 13th floor. Don’t underestimate the power of superstition.

While being able to predict Thanksgiving every year sounds great, it also means some holidays never moving again. Born on a Monday? Congratulations, your birthday is on Monday for the rest of your life!

There’s also the potential for disagreement over which day should come first. While international standard ISO 8601 defines the start of the week as Monday, the United States is one of a handful of countries that considers Sunday as the start. With today’s week-agnostic calendars, it’s not so much of an issue, but a calendar specifically designed around the days of the week could raise problems.

Antumi Toasijé, a Spain-based historian, has devised a workaround for that last issue. His New Universal Perpetual Calendar for Human Rights strips away the historical baggage of the Gregorian system and replaces it with days named after the continents, and months named after ideals:

The new calendar.
The new calendar.

With disagreements over how many continents there are, though — there’s no strict definition, and some places in southern Europe consider America to be one large continent — it might not be as universal an option as it first seems. Like Julius Caesar and the French revolutionaries discovered, designing a perfect calendar isn’t as easy as it seems.