In the aftermath of World War I, a League of Nations conference in Geneva sought to create a universal calendar to unite the world. However, my great-great-grandfather’s mission was to stop them. Calendrical disputes have existed since the beginning of time, and our modern calendar took centuries to establish. In 1923, the League of Nations proposed a total overhaul with a new calendar called the International Fixed Calendar (IFC) that consisted of 13 months of 28 days each. While the IFC promised uniformity, it posed a problem for Jewish people as it disrupted the Sabbath. The IFC gained popularity among businessmen, but ultimately, the calendar reform idea failed due to logistical challenges and religious objections.
https://www.washingtonpost.com/history/2023/11/04/battle-sabbath-13-month-calendar/