Show HN: Create new calendar systems to fix uneven months (opens in new tab)

I was playing around with divisors of numbers near 365 and realized you can generate a ton of valid calendar systems by picking a highly composite base (like 360) and treating the leftover days as end-of-year extra holidays.

365 is nearly prime (5×73), which is why our months are such a mess. But 360 has 24 divisors; enough to build clean hierarchies like 6-day weeks, 5-week months, 3-month quarters, 4 quarters/year + 5 holidays (6 on leap years). Every month identical, every date always the same weekday.

Built a small tool to explore all valid factorizations across different bases (336, 350, 354, 360, 364, 365), with a Gregorian comparison view that really highlights how arbitrary the current system is. Radial year visualization, work/rest analysis, season alignment, etc.

I've also added historical calendars, like the French Revolutionary calendar that was created in a similar sentiment.

Code facilitated by Claude Opus 4.6

Let me know what I should add, or if you catch a bug/mistaken logic!