en.wikipedia.org/…/International_Fixed_Calendar

The International Fixed Calendar (also known as the Cotsworth plan, the Cotsworth calendar, the Eastman plan or the Yearal)[1] was a proposed reform of the Gregorian calendar designed by Moses B. Cotsworth, first presented in 1902.[2] The International Fixed Calendar divides the year into 13 months of 28 days each.

Kodak actually used it from 1928 to 1989.