• 🔄 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

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

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

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

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

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

# Navigate to the project folder
cd SyncNotionGoogleCalendar

# Install dependencies
npm install

# Login to Google account with clasp
npm run login

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

# Push code to Google Apps Script
npm run push

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

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

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

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)

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

• ✅ "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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// 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}`);
}

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);
}

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

// Reset progress and start over
resetCleanupProgress();

• 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

This project is licensed under the MIT License.

Contributions to this project are welcome!

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

Please feel free to report details in GitHub Issues.