calendar-sync

Keep any pair of two Google Calendars in sync.

It can also use a public or a private (shared) calendar as source as long as the source calendar is added to the Google account's secondary / subscribed calendars list.

Installation

go get github.com/robertdolca/calendar-sync

In order to use calendar-sync as a command the go bin folder (~/go/bin) needs to be added to the PATH.

Authenticate accounts

calendar-sync auth

This will print link that can be used to authorize access to a Google account. If the calendars that need to be kept in sync are not owned by the same user or edit rights are restricted, this step can be repeated for any number of Google accounts.

List accounts and calendars

calendar-sync list

This will print a list of accounts that are authorized. For each account, a list of calendars will be displayed. The calendar list includes read only calendars and calendars the account is subscribed to.

Sync calendars

calendar-sync sync \
  -src-account accountA@gmail.com \
  -src-calendar dj3snc3c \
  -dst-account accountB@custom-domain.com \
  -dst-calendar jab1rgf \
  -title-override "Work event" \
  -copy-description \
  -copy-location \
  -include-not-going \
  -include-not-responded \
  -include-out-of-office \
  -include-tentative \
  -visibility private \
  -start-after 2006-01-02T15:04:05-07:00 \
  -exclude-title-regex '^(Busy \(personal\))|(❇️ Focus Time \(via Clockwise\))|(❇️ Lunch \(via Clockwise\))$' \
  -update-interval 2h

This will create events on the destination calendar if they are not already there. If a corresponding event exists it will be updated if necessary.

The sync action looks at events created or updated on the source calendar within the last 2 hours.

Delete synced events

calendar-sync clear \
  -account accountA@gmail.com \
  -calendar dj3snc3c

This will remove all synced events regardless of the source calendar.

For this operation to work well it requires the local sync DB to be preserved.

Internals

Google API app credentials

The CLI tool requires a Google API app that it will be used in the OAuth 2 flow. To create an app go to Developer Console.

Within the Google API app you need to create a OAuth 2.0 Client ID. The application type that should be selected is Desktop app.

Once the OAuth 2.0 Client ID is created the JSON credentials file should be downloaded and placed in the work directory under the name credentials.json.

The Google Calendar API needs to be enabled for the Google API app at.

Local database

The mapping between the source event id and the synced (copy) event id is maintained work directory and it is called sync.db.

Removing the database can lead to duplicate events being created.

Auth and refresh token

When a new account is authorized the auth token and the refresh token are stored in a file called tokens.json in the work directory.

To remove an authorized account or re-trigger the OAuth flow simply delete the tokens file.

When the file is read or update a lock file is created tokens.lock and it is cleaned up automatically.