13-Month Calendar

A calendar system with 13 months of equal length

About the 13-Month Calendar

This calendar system divides the year into 13 months of exactly 28 days each, making a total of 364 days. The extra day (365th) is called Year Day, and in leap years, an additional Leap Day is added.

Each month always starts on Monday and has exactly 4 weeks, making calendar calculations much simpler than the Gregorian calendar.

The 13th month is called Sol and comes between June and July.

Current date is highlighted in the calendar above.

Date Converter

Gregorian Date

13-Month Date

Format: TT.MM.JJJJ - Updates automatically

Conversion Results

Gregorian:Fri, Apr 3, 2026

13-Month:Invalid date

Month:-

Day:-

Note: The 13-month calendar has 13 months of 28 days each (364 days). Day 365 is "Year Day" and day 366 in leap years is "Leap Day" - both are not part of any month.