Guide
A Catholic liturgical calendar API for developers
A free JSON API for the Ordinary Form, 1962, and Dominican calendars, with Mass propers, the Office, saints, Scripture, prayers, and Mass times.
Updated 2026-10-17 · View resource
If you are building a parish website, a prayer app, or an AI agent, you need the right feast for a given date. Working that out means Easter tables, precedence rules, transferred solemnities, and national calendars. Gianna's Liturgy API does it for you.
What it returns
For a calendar, a region, and a date:
- the season and week, the lectionary cycles, and the psalter week;
- the day's celebration, with its rank and colour;
- commemorations and every saint whose feast falls on that date;
- whether it is a holy day of obligation;
- Mass propers and readings, and the hours of the Office where available;
- an optional explanation of why that celebration won.
Three calendars are supported: ordinary (General Roman Calendar),
traditional (1962), and dominican. Text always includes Latin, with English
on request.
A first call
Create a key under Settings, Developer access in the Gianna app. Then:
curl -s https://gianna.chat/liturgy/v1/calendars/ordinary/days/2026-12-25 \
-H 'Authorization: Bearer gianna_...'
The contract is published as OpenAPI 3.1 at /liturgy/v1/openapi.json.
Other APIs on the same key
- Scripture and prayers, returned word for word with their source.
- Church directory: churches and their Mass and Confession times, each with its source URL and the date it was checked.
- Saints and bishops: saint records and the lineage of bishops, with sources and change history.
No key at all
The feast-day calendars are free iCalendar feeds that need no account, at
https://gianna.chat/liturgy/v1/calendars/{ordinary|traditional|dominican}/feasts.ics.
See Catholic feast calendars.
Price and terms
The liturgy, Scripture, prayer, directory, and saint APIs are free with a Gianna account. The Terms do not allow reselling the data or copying it in bulk.
AI agents can use the same data through Gianna's MCP server. See Gianna for AI agents.
Household plans and the early-bird offer
The API is free. A household plan adds reminders, tasks, novenas, and the daily routines. The early-bird offer gives half price for your first year. Standard is $5 a month or $40 a year, normally $10 or $80. Pro, with voice notes and photo reading, is $10 a month or $80 a year, normally $20 or $160. One subscription covers the household, the first seven days are free, and nothing is charged during the trial. Prices checked on 17 October 2026; see gianna.chat for current terms, or start the free trial.