We once used to embrace a 13-month calendar, and some cultures still follow this format. So why are they 12 months instead of 13?

Unlike the 12-month Gregorian calendar used in most of the world, Ethiopia follows a 13-month system, which places it about seven to eight years behind the Western calendar.

New Calendar PropgressPresident George Eastman of the Eastman Kodak Co. last week received replies from the 1,000 businessmen whose opinions he had recently asked on the 13-month calendar he ...

Meeting in Manhattan last week, U. S. paper makers vigorously endorsed the often-proposed 13-month calendar with 28-day months and an extra summer month, Sol. "Inconsistencies" in the ...