Build a calendar for your world with odd months and a leap day

Your world has eight months of forty-five days and a week of six days, and the AI keeps quietly using ordinary months. Here is a tiny calendar that turns dates into day numbers and back, keeps the weekday running across the leap day, and finds festivals.

Why this works

Every date, however strange the months, is just a count of days from a starting point. Turn dates into that count and do all the adding there. Weekdays, festivals and leap days then follow from the count and need no special cases.

When not to use it

Skip it when your story only says things like "some years later" or when dates never matter to the plot. A made-up calendar is extra work for readers too, so use ordinary months where nothing depends on the difference.

In the full entry

• What to build, step by step
• Starting values and the reason for each
• 4 common mistakes and the fix
• A diagram of every state
• 37 lines of example code with 4 checks that pass
• How your AI shows you that it works

Say this to your AI

Use the Spielerando entry "Build a calendar for your world with odd months and a leap day" (read_entry in-world-calendar-with-leap-days) in my game. Build it step by step, and show me how you checked that it works.

Or skip this and connect the MCP: your AI then finds all of this by itself.Connect the MCP