Google AppScript: Automated OOO Calendar Sync

18 Apr, 2026

Instructions and script written by Al.
Reviewed, edited, and tested by Christine.

Limitations & Behavior

To ensure the script runs reliably, please keep the following in mind:

• One-Way Sync only: Changes made directly on the Shared Team Calendar will NOT sync back to your personal calendar. Always edit your OOO on your personal calendar.
• The "Move" Behavior: The script uses your Start Time as the unique anchor. If you drag an event to a different start time, the script will delete the old shared event and create a new one.
• Initial Sync: The script only looks 3 months into the future.
• Event Type: This script specifically looks for the "Out of Office" event type in Google Calendar. Standard "Busy" events are not synced.

Setup Instructions

1. Create the Script

1. Go to script.google.com.
2. Click New Project and name it "OOO Sync Tool".
3. Delete any existing code in the editor and paste the script provided below.

2. Enable the Calendar API (Required)

1. On the left sidebar, click the + icon next to Services.
2. Find and select Google Calendar API.
3. Click Add.

3. Personalize the Script

Edit the variables at the top of the script:

• MY_UNIQUE_TAG: Replace 'YOUR_UNIQUE_TAG_HERE' with a unique nickname (e.g., 'sync_jsmith').
• USER_NAME: Replace 'YOUR_NAME_HERE' with your name (e.g., 'Christine').
• SHARED_CALENDAR_ID: Replace 'YOUR_SHARED_CALENDAR_ID' with your shared calendar ID.

4. Run & Authorize

1. Click Run at the top.
2. Review and Allow permissions.
3. Check the Executions tab on the left to confirm the sync was successful.

5. Set the Hourly Automator

1. Click the Triggers (Clock icon) on the left sidebar -> + Add Trigger.
2. Function: syncOOO | Source: Time-driven | Type: Hour timer | Interval: Every hour.

The Script

(Remember to test it!)

// --- CONFIGURATION
const SHARED_CALENDAR_ID = 'YOUR_SHARED_CALENDAR_ID';
const MY_UNIQUE_TAG = 'YOUR_UNIQUE_TAG_HERE';
const USER_NAME = 'YOUR_NAME_HERE';

function syncOOO() {
  const primaryCalId = 'primary';
  const now = new Date();
  const futureLimit = new Date();
  futureLimit.setMonth(now.getMonth() + 3);

  console.info("Starting sync for period: " + now.toLocaleDateString() + " to " + futureLimit.toLocaleDateString());

  // 1. Fetch OOO entries from your personal calendar
  const oooEntries = Calendar.Events.list(primaryCalId, {
    timeMin: now.toISOString(),
    timeMax: futureLimit.toISOString(),
    eventTypes: ['outOfOffice'],
    singleEvents: true
  }).items || [];

  const sharedCal = CalendarApp.getCalendarById(SHARED_CALENDAR_ID);
  if (!sharedCal) {
    console.error("Could not find Shared Calendar. Check the SHARED_CALENDAR_ID.");
    return;
  }

  const sharedEvents = sharedCal.getEvents(now, futureLimit);
  const mySyncedEvents = sharedEvents.filter(e => e.getTag('sync_source') === MY_UNIQUE_TAG);

  // 2. UPDATE OR DELETE EXISTING SYNCED EVENTS
  mySyncedEvents.forEach(syncedEvent => {
    const matchingOOO = oooEntries.find(ooo => {
      const oooStart = new Date(ooo.start.dateTime || ooo.start.date).getTime();
      return oooStart === syncedEvent.getStartTime().getTime();
    });

    if (!matchingOOO) {
      console.warn("DELETING: " + syncedEvent.getTitle() + " (Event removed or start time changed on personal cal)");
      syncedEvent.deleteEvent();
    } else {
      const newTitle = USER_NAME + " " + matchingOOO.summary;
      const newEnd = new Date(matchingOOO.end.dateTime || matchingOOO.end.date);
      let changed = false;

      if (syncedEvent.getTitle() !== newTitle) {
        console.info("UPDATING TITLE: " + syncedEvent.getTitle() + " -> " + newTitle);
        syncedEvent.setTitle(newTitle);
        changed = true;
      }

      if (syncedEvent.getEndTime().getTime() !== newEnd.getTime()) {
        console.info("UPDATING TIME: Duration changed for " + newTitle);
        syncedEvent.setTime(syncedEvent.getStartTime(), newEnd);
        changed = true;
      }

      if (!changed) {
        console.log("NO CHANGE: " + newTitle + " is already up to date.");
      }
    }
  });

  // 3. CREATE NEW SYNCED EVENTS
  oooEntries.forEach(ooo => {
    const start = new Date(ooo.start.dateTime || ooo.start.date);
    const alreadyExists = mySyncedEvents.some(e => e.getStartTime().getTime() === start.getTime());

    if (!alreadyExists) {
      const title = USER_NAME + " " + ooo.summary;
      const end = new Date(ooo.end.dateTime || ooo.end.date);
      const newEvent = sharedCal.createEvent(title, start, end);
      newEvent.setTag('sync_source', MY_UNIQUE_TAG);
      console.info("CREATED: New event synced -> " + title);
    }
  });

  console.info("Sync process complete.");
}

↑ Back to top

#work