larzical

iCalendar (RFC 5545) — build and parse .ics — with zero dependencies.

Generate calendar invites and feeds that Google Calendar, Apple Calendar and Outlook accept, and parse the ones they send you. larzical implements the parts of RFC 5545 that matter in practice — and the details hand-rolled .ics generators get wrong: correct TEXT escaping, 75-octet line folding (multibyte-safe), UTC date-times, and CRLF endings.

Install

pip install larzical

Use

from larzical import Calendar, Event, Alarm
from datetime import datetime, date

cal = Calendar(prodid="-//Acme//App//EN", name="Team")
cal.add(Event(
    summary="Launch call",
    start=datetime(2026, 8, 1, 15, 0),
    end=datetime(2026, 8, 1, 16, 0),
    location="Zoom",
    description="Kickoff; agenda attached.",
    attendees=["a@x.com", "b@x.com"],
    alarms=[Alarm(trigger="-PT15M")],
))
cal.add(Event(summary="Company holiday", start=date(2026, 12, 25)))  # all-day

ics = cal.to_ical()               # a valid .ics string, folded + CRLF
Calendar.parse(ics)               # round-trips back to Events

Why it's correct

.ics files fail silently in calendar clients when the low-level rules are wrong. larzical is anchored to the spec:

• TEXT escaping (3.3.11) — , ; \ and newlines escaped/unescaped.
• Line folding (3.1) — content lines folded at 75 octets with CRLF , and never split in the middle of a multibyte character.
• Date-time (3.3.5) — UTC YYYYMMDDTHHMMSSZ; all-day as VALUE=DATE.
• Round-trip — Calendar.parse(cal.to_ical()) reconstructs the events.

Tests

python -m unittest discover -s tests -v   # 17 tests

The Larz stack

One of 60+ pure-Python, zero-dependency libraries at github.com/larz-scripter. Pairs with larzqr (add a scannable event QR) and larzemail (attach the invite to a MIME email).

License

MIT (c) larz-scripter