Meet “Mercedonius,” The Annoying Month That Used To Exist (Sometimes) Published January 26, 2011 There are many reasons to be thankful for the benefits of modern living: antibiotics, airplanes, velcro …. Another subtle but essential item is our calendar. It may have some frustrating moments, but consider how months used to work. Take heed of Mercedonius In the days of the Roman calendar, an intercalary month was added in leap years and a few other times as well. This month was called Mercedonius, but it was also known as Intercalaris. (The insertion of a leap day, week, or month into some years is called intercalation. Intercalation is done to align the calendar with the seasons or moon phases.) The name Mercedonius comes from the Latin word merces, which means “wages.” It got its name because workers were paid at the time of year Mercedonius occurred, around the month of Februarius. Why use an optional month? The addition of Mercedonius didn’t happen automatically. The decision was made by the high priest of the College of Pontiffs, who was also known as the Pontifex Maximus. The Pontifex Maximus, Latin for “greatest bridge-maker,” was the head honcho of the ancient Roman religion. The Pontifex Maximus was supposed to make the decision whether to include Mercedonius in any given year so that the calendar would correspond with the seasons. Politics, however, are said to have motivated his decision making. For example, Mercedonius was sometimes inserted to allow a government official to stay in office longer. The extra month gets the ax You can imagine the confusion that this caused. If you were living outside of Rome, you might have no idea what the current date was. In 46 bc, Julius Caesar introduced the Julian calendar and did away with Mercedonius. Can you guess the month that was named in honor of him? Find the answer here.