Somehow, for the first time ever, I recently heard the idea of the 13 month year and I sort of nodded my head in interest. Then I heard someone breakdown the history of calendars and it really blew my mind. Mainly the amount of thought that went into it and the incredible span of time it was revised and discussed!
The 13 month per calendar year (Mayan calendar) just makes so much sense as a web developer but somehow as a human it also seems hella mundane to have the same 28 day cycle repeated. Maybe that last day of the year party would make up for it though.
I quite like the hobbit calendar. 12 months of 30 days each, plus 5 (or 6) extra days that don't belong to a month and are celebration days. Mid-year day and the leap day don't have a day of the week, so each date always is the same day of the week.
The only disadvantage I can see is that you’d have your birthday in the same day of the week every year. If you are born on a Monday, you’ll celebrate on a Monday every year in your life.
I'm so familiar with the Gregorian calendar that I would prefer the International Fixed Calendar (13 months of 28 days + Leap Day and Year Day) with its yearly synchronization over the Mayan calendar.