Cal is three things working together: a CalDAV server that holds every faculty member's calendar, a shared Carillon that marks the hours and seasons, and a daemon called Calcifer that watches for upcoming events and delivers alarms to faculty via Matrix.
How It Works
Radicale
At the center is Radicale, a lightweight
CalDAV and CardDAV server. Every faculty member gets their own
principal — a private namespace at
cal.inquiry.institute/{username}/ where they can
create calendars, store events, and sync across devices.
Authentication is handled by Supabase SSO: the same credentials faculty use for the rest of the Institute's systems. Administrators (Custodian, Hypatia) have read/write access to all calendars.
Carillon
The Carillon is the Institute's shared, read-only calendar — a bell tower in data. It contains two kinds of recurring events: the daily bells that mark the rhythm of each day, and the Wheel of the Year that marks the turning of the seasons and the Institute's academic quarters.
Every faculty member is automatically subscribed to the Carillon. It also has a public feed anyone can add to their calendar app — no account required.
The Bells
Six daily bells. Floating time — they ring in your local timezone.
Floating time · no timezone · bells appear in your local time
The Wheel of the Year
Eight seasonal markers define four quarters of the academic year.
Calcifer
Calcifer 🔥 is the fire daemon. It runs alongside
Radicale, polling every faculty member's calendar every five minutes.
When an event has a VALARM trigger that falls within the
current window, Calcifer delivers a reminder to the faculty member's
private Matrix room.
The message includes the event name, time, and any notes — so faculty receive their calendar alarms as chat messages, even if their calendar app is closed. Calcifer also watches the Carillon: when a bell is about to ring or a seasonal marker approaches, every subscribed faculty member gets a gentle nudge.
Connect Your Calendar
Faculty can sync their personal calendar with any CalDAV client — Apple Calendar, GNOME Calendar, Thunderbird, DAVx5 on Android, and more. Events sync both ways: add on your phone, see it on your laptop.
| Server | https://cal.inquiry.institute |
|---|---|
| Username | Your inquiry.institute email |
| Password | Your Supabase password |
The Carillon is already in your calendar — it's auto-subscribed for all faculty. To add it to a non-faculty device, use the public feed:
| Carillon (public) | webcal://cal.inquiry.institute/subscribe/carillon.ics |
|---|
Under the Hood
Cal runs as a single container on Fly.io. Inside, Nginx handles TLS termination and routes traffic: browser requests to these pages, CalDAV protocol requests to Radicale. Supervisord keeps three processes alive — Nginx, Radicale, and Calcifer. Calendar data lives on a persistent Fly volume.