13 Month Calendar Calculator
Here’s a table summarizing the key information you need to know about a 13-month calendar:
| Feature | Description |
|---|---|
| Number of Months | 13 |
| Days per Month | 28 (4 weeks exactly) |
| Total Days | 364 (plus 1 or 2 extra days) |
| Extra Month Name | “Sol” (typically placed between June and July) |
| Extra Day(s) | “Year Day” (and “Leap Day” in leap years) |
| Weekday Consistency | Each date falls on the same day of the week every year |
| Month Start | Every month starts on a Monday |
| Month End | Every month ends on a Sunday |
| Quarters | Each quarter has 91 days (3 months of 28 days each) |
| Benefits | Easier financial comparisons, consistent scheduling |
| Challenges | Adoption, software updates, cultural adjustments |
| Historical Usage | Kodak used it from 1924 to 1989 |
| Origin | Proposed by Moses B. Cotsworth in 1902 |
| Popular Advocate | George Eastman (Kodak founder) |
Key points to remember:
- The calendar provides consistency, with each date always falling on the same weekday16.
- It simplifies financial calculations and comparisons across periods12.
- The extra month “Sol” is typically placed between June and July6.
- The “Year Day” (and “Leap Day” in leap years) are often placed outside the regular month structure6.
- While it offers benefits for business and scheduling, widespread adoption faces significant challenges35.
- The concept has been around since the 18th century, with various iterations proposed over time6.
This table provides a comprehensive overview of the 13-month calendar concept, its structure, benefits, and historical context.