Tonalpohualli Calendar

This project generates .ics calendar files for the Aztec tonalpohualli — the 260-day ritual count — for seven cities across North America. Each day’s entry includes the tonal (day-sign), trecena, and a full astronomical almanac: sun rise and set, moon phase and zodiac position, Venus visibility, and solar cycle tracking.

What it does

• Computes the Aztec day-sign using the Caso correlation
• Calculates sun, moon, and Venus rise/set times for any observer location
• Tracks the moon’s tropical and Vedic zodiac signs
• Outputs an importable .ics file for macOS Calendar, Google Calendar, or any iCal client

Why it matters

The tonalpohualli was systematically suppressed during the colonial period. This project restores it as a lived, daily practice — not as a museum piece, but as a working calendar that runs alongside the Gregorian one.

Source Code

The Python scripts that generate these calendars:

• aztec_calc.py — Tonalpohualli day-sign calculation (Caso correlation)
• astro_calc.py — Skyfield-based rise/set, moon phase, moon sign, and season tracking
• generate_ics.py — Builds the .ics files for each location

Subscribe to Calendars

Each calendar is available as a live subscription. Click the link for your city to automatically add it to your calendar app (Apple Calendar, Outlook, etc.).

• Tonalpohualli — Seattle
• Tonalpohualli — San Francisco
• Tonalpohualli — Mexico City
• Tonalpohualli — Guadalajara
• Tonalpohualli — Washington DC
• Tonalpohualli — Philadelphia
• Tonalpohualli — Boston