This 13-Month Calendar presents a structured and symmetrical approach to measuring time, based on the International Fixed Calendar concept.
Developed by Moses B. Cotsworth and introduced in 1902, this calendar was proposed as a reform of the traditional Gregorian system. It is also known under several names, including the Cotsworth Plan, Eastman Plan, and Yearal.
Unlike the modern calendar, this system organizes the year into 13 uniform months, each made up of 28 days. Every month contains exactly four weeks, resulting in a stable and predictable layout where weekdays never change from year to year.
How the 13 Month Calendar Works:
• 13 months per year
• 28 days in each month
• 4 weeks per month
• Total of 364 days
• One additional “Year Day” outside the weekly cycle
• Leap years include an extra leap day
The extra month is traditionally called Sol and is placed between June and July.
Materials: birch plywood 3 mm
Colors: rosewood, old oak
Dimensions: M - 30х22,5 сm/ 11.8x8.7"; L - 30х40 сm/ 11.8x15.8"
Personalization on the back side at the bottom right
Why This Calendar Is Unique:
• Perfect monthly symmetry
• Consistent weekly structure
• No shifting weekdays from year to year
• Historically proposed as a global calendar reform
Perfect For:
• Calendar and history enthusiasts
• Educational displays and learning spaces
• Office, study, or library décor
• Unique gifts for thinkers and planners
• Conversation-starting wall art
📌 This calendar is presented for educational and decorative purposes. It is not an official calendar system in modern use.
