You should know this ahead to fully enjoy that beauty of compact, mathematically sound week chart, and perhaps the accompanying momentary illusion that world makes sense again.
The next opportunity to enjoy most compact possible calendar page will be in 2038, so don’t miss it!
(Bonus: if you notice that 1st week is week 5 so apparently January 2027 also has 4 weeks–what gives? That’s because in ISO week numbering, first three days of January 2027 count as week 53 of 2026. In other words, week 1 of 2027 starts on January 4th.)
If your calendar starts with Sunday, this past February of 2026 was actually compact, and the next one is in 2037.
IMHO months add unnecessary complexity. In my own experimental calendar I use normal Gregorian year with ISO week numbers and then instead of months, I define seven “seasons” which are just 8-week periods (week 1 to 8, 9 to 16, etc.). Each season has 56 (8 x 7) days except for season 7, which is the only one that absorbs all the irregularities and typically has 29 days.
It could be pretty similar to 13-month calendar you described, but I decided to use larger unit and also remove ambiguity about meaning of “month” (all other units means the same thing as in Gregorian + ISO-week-numbering)—by simply abandoning that unit entirely.
(By the way, I always wanted to give these seasons names but my mind just goes blank whenever I try. I’m not very creative, I guess.)
Luckily there are many groups of 7 to draw inspiration from
https://www.explainxkcd.com/wiki/index.php/1417:_Seven
I was thinking of Crystal systems which would be cool because there’s 6 or 7 depending on convention. The only problem is that the “Monoclinic” would have 3-letter abbreviation of “Mon” which could be confused with abbreviation for Monday—I would challenge myself to find a way around it.
The XKCD thing is also great start. Continents would be nice, main-stream way of going about it. (I’m hopeful that people of Antarctica would not feel ripped off if they got the 7th season.)