Should The Year Have 13 Months?

Why do some months have 30 days, others 31, and then one only has 28? It doesn't make sense! Or so thought the man who reinvented the annual calendar in 13 months.

The 13-month, or Cotsworth, calendar

Monthly Review

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.

Entrepreneur George Eastman adopted the 13-month calendar at Eastman Kodak Company from 1928 to 1989.

Who Caught On?

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.

Key Facts In This Video

  1. The ancient Egyptians used Sirius to predict the annual flooding of the Nile, allowing them to become one of the first civilizations to use a solar calendar rather than a lunar one. 00:34

  2. Julius Caesar started the more precise Julian Calendar in 45 B.C. 02:07

  3. The Mayan calendar consists of 18 months of 20 days each, with five extra days at the end of the year. 05:20

Written by Curiosity Staff June 16, 2016

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