Calvin - Google Calendar CLI

Calvin is a command-line tool designed for quickly checking Google Calendar events. It provides a fast and efficient way to peek at your colleagues' or your own calendar—directly from your terminal—without opening a web browser.

Features

• Quick calendar checks: Retrieve and display events for a specified user and date in a readable format.
• Flexible date input: Supports relative dates like today, tomorrow, and next <weekday>, as well as specific dates in YYYY-MM-DD format.
• User-friendly output: Presents event summaries, times, and attendees in a clear, color-coded terminal display.
• Default domain configuration: Allows you to simply type a username instead of a full email address.
• Secure access: Uses Google OAuth 2.0 for accessing Google Calendar.
• Timezone awareness: Displays event times in the calendar's timezone or, optionally, in your local timezone.

Usage

The basic syntax for using Calvin is:

calvin [flags] <username> [date]

• <username>: The username or email address of the calendar to view. If only a username is provided, Calvin will append the default_domain from your configuration. You can provide a default username that will be used if you omit the username.
• <date> (optional): The date for which to retrieve events. Acceptable formats include:
  • (Omitted): Show events for today.
  • tomorrow: Show events for tomorrow.
  • next <weekday>: Show events for the next occurrence of the specified weekday (e.g., next monday).
  • week: Show events for the current week (Monday through Sunday).
  • next week: Show events for the next week (next Monday through Sunday).
  • YYYY-MM-DD: Show events for a specific date in ISO 8601 format (e.g., 2025-12-25).

Flags

• --local: Use your local timezone for displaying event times instead of the calendar's timezone.

Examples

1. Check today's events for bob.smith (using default domain):

calvin bob.smith

Expected output:

Listing events for 2025-01-30 (bob.smith@example.com) [tz: Europe/Oslo]...
- Storage #1 talk       [13:00 --> 13:30]  [john.doe, ...]
- Storage #2 doc review  [14:30 --> 15:30]  [jane.doe]
- Company Update January [17:00 --> 18:00]  []

2. Check tomorrow's events for jane.doe:

calvin jane.doe tomorrow

3. Check events for john.doe next monday:

calvin john.doe next monday

4. Check events for carol@example.net on a specific date (2025-12-25):

calvin carol@example.net 2025-12-25

5. Check today's events for bob.smith using your local timezone:

calvin --local bob.smith

Expected output:

Using local timezone: Local
Listing events for 2025-01-30 (bob.smith@example.com) [tz: Europe/Oslo]...
- Storage #1 talk       [13:00 --> 13:30]  [john.doe, ...]
- Storage #2 doc review  [14:30 --> 15:30]  [jane.doe]
- Company Update January [17:00 --> 18:00]  []

6. Check events for the current week for alice.smith:

calvin alice.smith week

Expected output:

Listing events for the week of 2025-01-27 to 2025-02-02
--------------------------------------------------
Listing events for 2025-01-27 (alice.smith@example.com) [tz: Europe/Oslo]...
- Weekly Planning      [09:00 --> 10:00]  [team, ...]
- Project Review       [14:00 --> 15:00]  [manager]
--------------------------------------------------
Listing events for 2025-01-28 (alice.smith@example.com) [tz: Europe/Oslo]...
- Team Standup         [09:30 --> 10:00]  [team, ...]
- Client Meeting       [13:00 --> 14:00]  [client, ...]
--------------------------------------------------
...

7. Check events for next week for dave.jones:

calvin dave.jones next week

Installation

Prerequisites

• Go: Version 1.20 or higher is required. Download it from https://go.dev/dl/.

Install Calvin

Run the following command to install Calvin:

go install github.com/perbu/calvin@latest

This command downloads and installs the calvin executable into your $GOPATH/bin directory. Make sure that $GOPATH/bin is in your system's PATH so you can run Calvin from anywhere.

Configuration

To use Calvin, you must configure access to the Google Calendar API and set up a configuration file.

1. Create OAuth Credentials

Calvin uses Google's OAuth 2.0 for secure access. Follow these steps to create the necessary credentials:

1. Go to the Google Cloud Console.
   • If you don't have a project, create one.
2. Enable the Google Calendar API:
   • Navigate to APIs & Services → Enabled APIs & Services.
   • Click + ENABLE APIS AND SERVICES.
   • Search for Google Calendar API and enable it.
3. Create OAuth 2.0 credentials:
   • In the left-hand menu, click APIs & Services → Credentials.
   • Click + CREATE CREDENTIALS and choose OAuth client ID.
   • If prompted, configure the consent screen:
     • Click CONFIGURE CONSENT SCREEN.
     • Choose External (or Internal if using a Google Workspace account).
     • Fill in the required fields (App name, User support email, Developer contact info). Minimal information is sufficient for personal use.
     • Click SAVE AND CONTINUE (bypassing optional steps) and return to the dashboard.
   • Click + CREATE CREDENTIALS → OAuth client ID again.
   • Select Desktop application as the Application type.
   • Name it (e.g., "Calvin CLI") and click CREATE.
   • Click DOWNLOAD JSON to save your credentials as credentials.json.
4. Place the credentials.json file:

   • Create a directory named .calvin in your home directory:

     mkdir ~/.calvin

   • Move the downloaded credentials.json file into the ~/.calvin directory.

2. Create a Config File

Create a config.json file in the ~/.calvin directory to set your default configurations:

1. Open (or create) the file with your preferred editor:

   nano ~/.calvin/config.json

2. Paste the following JSON content into the file and save it:

   {
     "default_domain": "example.com",
     "default_username": "bob.smith"
   }

• default_domain (optional): Set this to your organization's domain. This lets you simply use a username (e.g., calvin bob.smith) instead of a full email address. If you work with multiple domains, you can leave this blank and always specify full email addresses.

Running Calvin for the First Time

When you run Calvin for the first time, it will launch a browser window to authenticate with Google. Follow the on-screen instructions to grant Calvin permission to access your Google Calendar. Once authenticated, Calvin saves a token for future use so that you won’t need to log in every time.