ICS to CalDAV synchronisation

Downloads a calendar in ICS format and uploads it to a CalDAV server, regularly. Your employee, school, or whoever shares a calendar as a link to an ICS file, and you'd like to have it on another CalDAV server? Look no further.

Standalone usage

Install the script with pip install ics_caldav_sync (or, if installing from source, pip install .) and run ics_caldav_sync script which should be on your PATH now. Python 3.10 or higher is required.

There also exist Dockerfile and docker-compose.yml files so you can run it on your Docker server.

The Docker images are published to Docker Hub, repository przemub/ics_caldav_sync tagged by short commit hashes and versions.

Set the settings as environment variables:

• For Google Calendar, you can ignore DTSTAMP (changes with every download of the ICS) and SEQUENCE (reported to change randomly).

Library usage

This script can be also used as a library in your Python script using ICSToCalDAVSync class and its synchronise method.

from ics_caldav_sync import ICSToCalDAVSync

sync = ICSToCalDAVSync(
    remote_url="https://example.com/calendar.ics",
    local_url="https://caldav.example.com",
    local_calendar_name="My Calendar",
    local_username="username",
    local_password="password",
    # local_tls_verify=True,
    # remote_username="",
    # remote_password="",
    # remote_auth="basic|digest",
    # remote_tls_verify=True,
    # sync_all=False,
    # keep_local=False
    # timezone=None,
    # ignored_compare_fields=[]
)

sync.synchronise()

Examples

Command-line usage

ics_caldav_sync can be used from the command line when installed with pip. An example:

REMOTE_URL=https://example.com/path/to/calendar_file.ics \
  LOCAL_URL=https://example.net/caldav \
  LOCAL_CALENDAR_NAME="My Calendar" \
  LOCAL_USERNAME=myusername \
  LOCAL_PASSWORD=mypassword \
  ics_caldav_sync

Docker

You can also do the same as a Docker one-liner - to avoid installing dependencies yourself.

docker run --rm \
  -e REMOTE_URL=https://example.com/path/to/calendar_file.ics \
  -e LOCAL_URL=https://example.net/caldav \
  -e LOCAL_CALENDAR_NAME="My Calendar" \
  -e LOCAL_USERNAME=myusername \
  -e LOCAL_PASSWORD=mypassword \
  przemub/ics_caldav_sync

Docker Compose

When setting up a long-running, periodic sync, Docker Compose can be helpful.

This example also shows settings needed by a CalDAV server Baïkal.

services:
  ics_caldav_sync:
    image: ics_caldav_sync
    restart: unless-stopped
    environment:
      - REMOTE_URL=https://example.com/path/to/calendar_file.ics
      - LOCAL_URL=https://baikal.myserver.com/dav.php/
      - LOCAL_CALENDAR_NAME=My Calendar
      - LOCAL_USERNAME=myusername
      - LOCAL_PASSWORD=mypassword
      - LOCAL_AUTH=digest  # Required by Baikal - try removing if getting Unauthorized error
      - SYNC_EVERY=30 minutes

Tested with

On the local side (CalDAV server):

• Baïkal
• Radicale
• xandikos

On the remote site (ICS file generator):

• Google Calendar
• Microsoft Outlook

Please feel free to open a PR against this section to add your configuration!

Rationale

In my case, my new shiny Bluetooth wristwatch, Casio Edifice ECB-10, did not support synchronisation with calendar subscriptions. And so this script was created.