Around the turn of the 20th century, Moses B. Cotsworth, an accountant for the British Railway, was running into issues with the calendar. Those issues hardly need explaining: every month has a different number of days and weeks, and virtually nothing stays constant from one year to the next. So instead of struggling, he invented a new calendar. In Cotsworth's design, there are 13 months of exactly 28 days. Every month has four weeks, and every date has a dedicated weekday: the 1st is always a Sunday; the 13th, interestingly, is always a Friday. Cotsworth's 13th month is called Sol, for the summer solstice, and lands between June and July when the solstice occurs. The leap day was also reassigned from its previous role in February to a place at the end of Sol. To round out 365 days, Cotsworth added Year Day after the 28th of December as a global holiday that belonged to no individual month.

Though he tried passionately to get world leaders to adopt his calendar, no one of importance took notice, except for one man: the founder of Kodak, George Eastman. Kodak implemented the 13-month calendar in 1924, and it stayed in place organizing the company's finances and production all the way until 1989. Though the 13-month calendar may sound strange, it's no stranger than the Gregorian calendar we use today, which has gone through numerous alterations to stay on schedule through the millennia.