Google Calendar Synchronisation

Pyhton script that synchronises calendars between two Google Accounts.

Python 3 is required.

Security warnings

• This application copies data from one Google account calendar to a different one. Please, make sure your that you are not sharing sensible data and confirm it with your organisation.
• Make sure you don't expose any credential information (.json and .pickle files are ignored on .gitignore file to prevent this.

How to install

pip3 install -r requirements.txt

Run the application

To run the application, you have to generate as many credential.json files as Google Account you want to manage. To create those files, read the credentials section.

The first time the application is run, a pop-up appears to verify your credentials. If a message indicates that Google has not verified the application, click on Continue.

Allow the permissions to edit calendars.

If you get a message like this, follow the instructions on it to enable calendar API.

gcallist command

Let's suppose that we have already downloaded the credentials file to the root folder of this repository with a name myaccount.credentials.json. To list all the calendar ids and names from this account, run:

python3 gcallist.py mmyacount

This will print something like:

ID: addressbook#[email protected]  NAME: Birthdays
ID: en.spain#[email protected]  NAME: Holidays in Spain
ID: [email protected]  NAME: [email protected]

This is useful to know the ID of the source and target calendars in gcalsync commmand

gcalsync command

This command copies event from a source calendar to a target one. Let's suppose we created two credentials files in the root folder:

account1.credentials.json
account2.credentials.json

The following command will copy all the events from one calendar (source) to another one (target)

python3 gcalsync.py account1 "calendar-id-21" account2 "calendar-id-33" 1d

• account1 is the source account. The name should match with any XXX.credentials.json file.
• calendar-id-21 is the id from the source calendar. To know this id, see gcallist section.
• account1 is the target account. The name should match with any XXX.credentials.json file.
• calendar-id-21 is the id from the target calendar. To know this id, see gcallist section.
• 1d means that it will copy events from current time to the end of this day. Other possible values
  • 2d: will copy events from current timme to the end of tomorrow. 3d, 4d and so on are also possible.
  • 1w: will copy events from current time to the end of this week.
  • 2w: will copy events from current time to the end of next week. 3w, 4w and so on are also possible.

NOTE: If you use "primary" as calendar id, you will use the account main calendar. Eg. this command would copy events from the main calendar in account1 to the main calendar in account2

 python3 gcalsync.py myaccount primary myaccount primary 1d 

NOTE: You can also copy events from calendars inside the same account. Eg. this command would copy events from calendar with id c-1 to calendar with id c-2, both in the account myaccount

 python3 gcalsync.py myaccount "c-1" myaccount "c-2" 2d 

NOTE: The command can safely be executed several times. All the already synchronised events will be removed from the target calendar and recreated.

NOTE: By default, the name, description and location of the events are not copied to prevent exposing sensible data, but copying of sensible data can be enabled by adding the parameter --copySensibleData at the end. Eg.

python3 gcalsync.py account1 "calendar-id-21" account2 "calendar-id-33" 1d --copySensibleData

NOTE: Use the --colorId argument to pick a color number (try values 1, 2, 3.. and so on) in order to visually distinguish the synced events:

python3 gcalsync.py account1 "calendar-id-21" account2 "calendar-id-33" 1d --colorId 5

See the colors resource for more details and possible values.

What if my organisation does not allow Google API?

In that case, it is still possible to use gcalsync. Imagine that source account account1 does not allow Google API. In that case, we won't be able to create the credentials file to copy events from account1.

But we can make a calendar from account1 visible in account2 by following these steps:

• Go to calendars.
• Open Settings and sharing for the calendar you want to share.

• Add a new entry in Share with specific people including the email of the target account (account2 in the example). You can select the level of visibility for those events (take into account your organisation security guidelines).

From this moment, you will have a copy from your calendar in your target account, so you will be able to copy events from it to your main calendar (or other account calendar) just using the credentials for account2.

python3 gcalsync.py account2 "calendar-copies-from-account-1" account2 "target-calendar" 1d 

Credentials

1. Go to https://console.cloud.google.com/apis/credentials.
2. Set up a new project.

3. Choose any name (gcal3 in the example) and don't select any organisation.

4. Select OAuth consent screen, select External as User Type and click on create.

5. Set as app name to any name, eg. gcalsync. Only this name, user support email and developer contact information are mandatory.

6. Click on Save and Continue.

7. Then, in scopes, select Add or remove scopes and in Manually add scopes put this:

https://www.googleapis.com/auth/calendar
https://www.googleapis.com/auth/calendar.events

8. Click on Add to table and then in Update.

9. Click on Save and Continue

10. In test users, add your own user (Google email).

11. Click on Save and Continue.

12. Go to Credentials, Create Credentials, select OAuth client ID.

13. Set application type to Desktop app and choose any application name.

14. Once created, click on the created credential.

15. Click on the credential and download json file to the gcalsync directory, with a name format like this:

name.credentials.json

where name can be chosen by you to identify your account.

16. Repeat all the previous steps if you want to manage other accounts.

Running automated in a crontab

You can use a crontab to automatically execute calendar sync in the background.

In a console, enter:

crontab -e

This will open an editor (vi). To append a line, type Go and paste:

1 * * * * * /opt/homebrew/bin/python3 /Users/kfleerko/code/gh/klausfl/gcalsync/gcalsync.py tw "[email protected]" tw primary 14d --colorId 5

Press escape and type :x! to exit.

Possible improvements

• Allow bi-directional synchronisation. Not very far away.
• Publish a command to avoid having to clone the repo. See this link.