Citylab:

The 13-month calendar worked so well at Kodak that the company used it until 1989, 57 years after Eastman committed suicide (a businessman to the end, his ashes are buried at Kodak’s old industrial complex). “I loved it,” says John Cirocco, a former Kodak employee who worked at the company in the late ’80s as a tech advisor. “It was a major piece of financial applications, and from a financial perspective it made the ability to compare sales periods a hell of a lot easier.”

Besides the occasional carryover (Kodak’s 1989 financial year began on December 26, 1988), overlapping a 13-month calendar with the Gregorian one came with surprisingly few hiccups. “After I got hired, it took about a week to adjust to,” Cirocco tells us. “When I first got there they explained it to me and I was like, ‘Oh, my God, this is brilliant!'” In fact, the former Kodak employee remains fond of the calendar to this day. “I’ve tried to recommend it at two places I’ve worked at since then. The feedback is always, ‘We can’t, this [12-month calendar] is how it’s always been done.'”