Calendar Contraptions

The machines we count days with. ← Workbench

A day, a moon and a year never divide evenly, so every calendar in history is a contraption: a hack that balances arithmetic, astronomy and politics — and breaks somewhere interesting. Each piece in this corner takes one way of counting days apart: a working converter, and the story of where it cheats.

Pieces

• One day, five counters the same date as a Julian Day Number, Julian date, ISO week, Maya Long Count and French Republican date — live
• The days have names all 360 named days of the French Republican year — plants, minerals, animals, tools — find yours · live
• Ten days that never happened October 1582, the Gregorian reform, and why the Orthodox Christmas is in January · live
• Weeks don't fit the ISO week calendar, its secret year, the 53-week trap and the three attempts to build a week that fits · live
• Mayan arithmetic the long count as a machine: five dials, one bent gear, zero as a shell — push the odometer yourself · live
• Reforms that never happened the World Calendar, Comte's great men, the Hanke–Henry echo and the arithmetic patch France never ran · live
• Unix time is a calendar the epoch, the leap seconds and the 2038 cliff — the calendar hiding in every computer · coming next

Why bother

Because a calendar is the rare machine that everyone uses and nobody looks at. Its gears are leap rules and moon phases and a pope's arithmetic; its bugs caused riots; its version history includes guillotines and ten vanished days. None of the counters here is wrong — that is the quiet lesson. They are all counting the same days, and they all had a good reason.