Sync Notion-GoogleCalendar

🇯🇵 日本語版 README はこちら / Japanese README

A Google Apps Script project that provides bidirectional synchronization between Notion databases and Google Calendar.
Automatically sync tasks and schedules managed in Notion to Google Calendar.

✨ Features Overview

• 🔄 Auto Sync: Automatically synchronizes Notion items with "Schedule" tags to Google Calendar every 15 minutes
• 📅 Date Processing: Supports all-day events, timed events, and period events
• 🛡️ Duplicate Prevention: Prevents duplicate creation using Event IDs
• ↔️ Bidirectional Sync: Reflects changes and deletions in Notion to the calendar

🚀 Setup

1️⃣ Prerequisites

• Node.js (v16 or later)
• npm
• Google Account
• Notion Account

2️⃣ Notion API Configuration

Creating Notion Integration

1. Access Notion Developers
2. Click "+ New integration"
3. Enter integration name (e.g., GoogleCalendar-Sync)
4. Click "Submit"
5. Copy and save the Internal Integration Token

Obtaining Database Information

1. Open the Notion database to be synchronized
2. Get the Database ID from the URL
   • https://notion.so/workspace/{database-id}?v={view-id}
   • The {database-id} part is the database ID
3. Get the "Schedule tag" Page ID
   • Click on the Schedule tag → Get the page ID from the URL

Database Sharing Settings

1. Click "⋯" at the top right of the database → "Add connections"
2. Select and add the created integration

3️⃣ Google APIs Configuration

Google Cloud Console Setup

1. Access Google Cloud Console
2. Create a new project or select an existing one
3. Enable Google Calendar API
   • "APIs & Services" → "Library"
   • Search for "Google Calendar API" and enable it
4. Enable Google Apps Script API
   • Follow the same procedure to enable

4️⃣ Building Google Apps Script Project with npm and clasp

Installing and Authenticating clasp

# Navigate to the project folder
cd SyncNotionGoogleCalendar

# Install dependencies
npm install

# Login to Google account with clasp
npm run login

Creating and Deploying Google Apps Script Project

# Create a new GAS project (first time only)
npm run create

# Push code to Google Apps Script
npm run push

5️⃣ Google Apps Script Configuration

Setting Script Properties

1. Access Google Apps Script
2. Open the created project
3. Left menu "Project Settings" → "Script properties"
4. Add the following properties:

Property Name	Value	Description
NOTION_API_KEY	secret_xxxxx...	Notion Internal Integration Token
NOTION_DATABASE_ID	xxxxxxxxx...	Target Notion Database ID
SCHEDULE_TAG_ID	xxxxxxxxx...	"Schedule" tag Page ID
CALENDAR_ID	primary or specific calendar ID	Target Google Calendar (optional)

Enabling Required API Services

1. Left menu "Services"
2. Enable Google Calendar API (select v3)

6️⃣ Notion Database Configuration

To ensure proper synchronization, the following properties are required in the Notion database:

Property Name	Type	Required	Description
Title	Title	✅	Event title
Action Day	Date	✅	Event date and time
Tags	Relation	✅	Relation containing "Schedule" tag
Status	Status	❌	Task status
Event ID	Text	❌	Google Calendar Event ID (automatically set)
URL	URL	❌	Related links

📖 Usage

1️⃣ Initial Setup Execution

Execute initial setup in Google Apps Script editor:

// Execute initialization function (first time only)
initialize();

This function performs the following:

• Verifies script properties
• Tests Google Calendar API connection
• Sets up automatic sync trigger (15-minute intervals)

2️⃣ Schedule Management in Notion

Creating Schedule Items

1. Create a new page in the Notion database
2. Enter event name in Title
3. Set date and time in Action Day:
   • All-day event: Date only (e.g., 2023-12-25)
   • Timed event: Specify date and time (e.g., 2023-12-25 14:30)
   • Period event: Set start and end date/time
4. Add "Schedule" tag to Tags

Sync Target Conditions

• ✅ "Schedule" tag is included in Tags
• ✅ Action Day is set
• ✅ Action Day is within sync range (30 days ago to 90 days ahead)
• ❌ Items not meeting the above criteria are excluded from sync

3️⃣ Automatic Sync Operation

Sync Timing

• Automatic sync: Executes every 15 minutes
• Manual sync: Execute manualSync() in Google Apps Script editor

Synchronized Operations

Notion Operation	Google Calendar
📝 Create new	➕ Create event
✏️ Change title	🔄 Update event
📅 Change date/time	🔄 Update event
❌ Remove Schedule tag	🗑️ Delete event
🗑️ Delete page	🗑️ Delete event

4️⃣ Event Format Examples

All-Day Event

Title: Meeting Preparation
Action Day: 2023-12-25
→ Google Calendar: 12/25 all-day event

Timed Event

Title: Team Meeting
Action Day: 2023-12-25 14:00 → 2023-12-25 15:30
→ Google Calendar: 12/25 14:00-15:30

Multi-Day Event

Title: Business Trip
Action Day: 2023-12-25 → 2023-12-27
→ Google Calendar: 12/25-12/27 all-day event

5️⃣ Sync Status Verification

Tracking with Event ID

• Synchronized Notion pages automatically have Event ID set
• This ID manages the connection with Google Calendar
• Pages with Event ID are already synchronized

Checking Sync Logs

Check sync status in Google Apps Script editor execution logs:

=== Sync Process Started ===
Retrieved 3 schedule items from Notion
Retrieved 5 events from Google Calendar
=== Sync Process Completed ===
Created: 1, Updated: 1, Deleted: 0

🔧 Troubleshooting

❌ Common Errors and Solutions

1. Notion API Connection Error

Error: Notion API Error (401): Unauthorized

Causes and Solutions:

• ❌ NOTION_API_KEY is not set correctly
  • ✅ Verify the Internal Integration Token obtained from Notion Developers
  • ✅ Set correctly in Google Apps Script script properties
• ❌ Integration not added to database
  • ✅ Notion database → "⋯" → "Add connections" to add integration

2. Unable to Retrieve Schedule Items

Log: Retrieved 0 schedule items from Notion

Causes and Solutions:

• ❌ SCHEDULE_TAG_ID is incorrect
  • ✅ Open "Schedule" tag page and verify page ID from URL
  • ✅ Page ID is a 32-character string including hyphens
• ❌ No items with "Schedule" tag in database
  • ✅ Create items in Notion and add "Schedule" tag
  • ✅ Verify that Action Day is also set

3. Google Calendar API Connection Error

Error: Google Calendar API is not enabled

Causes and Solutions:

• ❌ Calendar API not enabled in Google Apps Script
  • ✅ Google Apps Script → "Services" → Add Google Calendar API v3
• ❌ Calendar API disabled in Google Cloud Console
  • ✅ Google Cloud Console → APIs & Services → Library → Enable Google Calendar API

4. Sync Not Executing

Log: Trigger not set

Causes and Solutions:

• ❌ Periodic execution trigger not set
  • ✅ Google Apps Script → Triggers → Verify 15-minute interval trigger for syncNotionWithGoogleCalendar function
  • ✅ Or execute initialize() function to automatically set trigger

5. Date Format Error

Error: Valid Action Day is not set

Causes and Solutions:

• ❌ Notion Action Day property is empty
  • ✅ Set appropriate date in Notion Action Day
• ❌ Action Day format is incorrect
  • ✅ All-day: 2023-12-25
  • ✅ Timed: 2023-12-25T14:30:00
  • ✅ Period: Set start date → end date

6. Permission Error

Error: Insufficient permissions

Causes and Solutions:

• ❌ Calendar scope insufficient in Google Apps Script
  • ✅ Approve required permissions when executing script
  • ✅ Click "Review permissions" on "Authorization required" screen

7. Calendar Usage Limits Exceeded

Error: API call to calendar.events.insert failed with error: Calendar usage limits exceeded.

Causes and Solutions:

• ❌ Events outside the sync range were repeatedly created, exceeding Google Calendar API quotas
  • ✅ Run cleanupDuplicateEvents() to delete duplicate events (run repeatedly until complete)
  • ✅ Update to the latest version to apply the date range filter fix

🔍 Debugging Methods

Checking Logs

1. Google Apps Script → "Execute" → Run any function
2. Check error details in "Execution log"
3. Add Logger.log() for detailed debugging

Manual Testing

// Testing individual functions
function testNotionConnection() {
  const items = getNotionScheduleItems();
  Logger.log(`Number of items retrieved: ${items.length}`);
  items.forEach(item => Logger.log(item.title));
}

function testCalendarConnection() {
  const events = getGoogleCalendarEvents();
  Logger.log(`Number of events retrieved: ${events.length}`);
}

Verifying Configuration Values

function checkConfiguration() {
  const config = {
    apiKey: CONFIG.NOTION_API_KEY ? 'Set' : 'Not set',
    databaseId: CONFIG.NOTION_DATABASE_ID ? 'Set' : 'Not set',
    scheduleTagId: CONFIG.SCHEDULE_TAG_ID ? 'Set' : 'Not set'
  };
  Logger.log(config);
}

Cleaning Up Duplicate Events

// Detect and delete duplicate events (resumable, run repeatedly until complete)
cleanupDuplicateEvents();

// Reset progress and start over
resetCleanupProgress();

⚠️ Important Notes

• Rate Limits: Notion API allows maximum 3 requests per second
• Time Zone: Set to Asia/Tokyo by default
• Sync Range: Only targets events from 30 days ago to 90 days in the future
• Duplicate Prevention: Prevents duplicate creation through Event ID linking

🗃️ Notion Database Items Used in This Project

📄 License

This project is licensed under the MIT License.

🤝 Contributing

Contributions to this project are welcome!

• 🐛 Bug reports
• 💡 Feature suggestions
• 🔧 Pull requests

Please feel free to report details in GitHub Issues.