copyCalendarEvents.gs

const config = {
  '[email protected]': {
    prefix: 'Source',
    color: CalendarApp.EventColor.PALE_RED,
    visibility: 'private'
  },
  '[email protected]': {
    target: 'Other Calendar Name',
    attendees: false,
    prefix: 'Company',
    filterColor: CalendarApp.EventColor.YELLOW,
  },
};

function getCalendars() {
  let pageToken;
  let calendars = [];

  do {
    const list = Calendar.CalendarList.list({pageToken, showHidden: true});
    pageToken = list.pageToken;
    calendars = calendars.concat(list.items);
  } while (pageToken);

  calendars.sort(compareUsing(sortableId));
  return calendars;
}

function compareUsing(fn) {
  return ((a, b) => fn(a).localeCompare(fn(b)));
}

function sortableId(calendar) {
  return calendar.id.split('@').reverse().join('@');
}

function colorName(id) {
  return Object.keys(CalendarApp.EventColor).find(c => CalendarApp.EventColor[c] == id);
}

function onCalendarChanged(trigger) {
  copyEvents(trigger.calendarId);
}

function copyAll() {
  Object.keys(config).forEach(copyEvents);
}

// avoid multiple scripts running at the same time
function getLock(retries = 3) {
  try {
    const lock = LockService.getScriptLock();
    lock.tryLock(1000);
    return lock;
  } catch (err) {
    if (retries) {
      return getLock(retries - 1);
    }

    throw new Error('Could not obtain script lock');
  }
}

function copyEvents(sourceId) {
  const lock = getLock();
  if (!lock.hasLock()) {
    console.log('Process already running');
    return;
  }

  if (!config[sourceId]) {
    console.log('No config for ' + sourceId);
    return;
  }

  console.log('Copying events from ' + sourceId);
  const summaryPrefix = (config[sourceId].prefix ? `[${config[sourceId].prefix}] ` : '');
  const syncDays = config[sourceId].syncDays || 14;

  // set target calendar
  let targetId = Session.getActiveUser().getEmail();
  if (config[sourceId].target) {
    targetId = getCalendars().find(c => c.summary == config[sourceId].target).id;
  }

  // start and end dates
  let startDate = new Date();
  let endDate   = new Date();
  endDate.setDate(startDate.getDate() + syncDays);

  // delete and recreate in case things move
  cleanup(targetId, syncDays, summaryPrefix);

  // get all events
  const listResponse = Calendar.Events.list(sourceId, {
    timeMin: startDate.toISOString(),
    timeMax: endDate.toISOString(),
    singleEvents: true,
  });

  const targetEventIds = Calendar.Events.list(targetId, {
    timeMin: startDate.toISOString(),
    timeMax: endDate.toISOString(),
    singleEvents: true
  }).items.map(e => e.id);

  // loop over and copy
  listResponse.items.forEach(function (event) {
    const summary = (event.summary || 'busy');
    console.log('Copying event: ' + summary + ' (' + (event.start.dateTime || event.start.date) + ')');

    if (targetEventIds.includes(event.id)) {
      console.log('Event is already shared with the target calendar, ignoring');
      return;
    }

    if (config[sourceId].filterColor && config[sourceId].filterColor != event.colorId) {
      console.log('Ignoring event with colour: ' + (colorName(event.colorId) || 'default'));
      return;
    }

    try {
      Calendar.Events.insert({
        start:          event.start,
        end:            event.end,
        summary:        summaryPrefix + summary,
        description:    event.description,
        conferenceData: event.conferenceData,
        colorId:        config[sourceId].color || 0,
        visibility:     config[sourceId].visibility || event.visibility || 'default',
        attendees:      event.attendees ? [{
          email:          targetId,
          responseStatus: event.attendees.find(a => a.self).responseStatus
        }] : []
      }, targetId, {
        conferenceDataVersion: 1
      });
    } catch (err) {
      console.log(err.toString());
    }

    Utilities.sleep(500);
  });

  lock.releaseLock();
  console.log('All events copied');
}

function cleanup(targetId, daysAhead, titlePrefix) {
  let calendar = CalendarApp.getCalendarById(targetId);
  
  let startDate = new Date();
  let endDate   = new Date();
  endDate.setDate(startDate.getDate() + daysAhead);

  calendar.getEvents(startDate, endDate).forEach(function (event) {
    if (event.getTitle().startsWith(titlePrefix)) {
      console.log('Deleting event: ' + event.getTitle() + ' (' + event.getStartTime().toLocaleString('en-GB') + ')');
      try {
        event.deleteEvent();
      } catch (e) {
        console.log('Failed to delete: ' + e);
      }
      
      Utilities.sleep(500);
    }
  });
}

Copy Calendar Events

This Apps Script copies calendar events from any number of source calendars. This can be useful
when use multiple work calendars and need colleagues to see your true availability.

Note

This script currently deletes events from your target calendar and recreates them. Not only is this a naïve approach, it is risky that it might delete events not part of the sync that just happen to have a similar title.

Installation

1. In your source calendar, click the ⋮ actions button next to the calendar, and click Settings and sharing.
2. Scroll to "Share with specific people", and add the email address of your target calendar.
3. Choose "See all event details". (This is needed to replicate the status / conference info to your target calendar.)
4. You will receive an email to your target account sharing this calendar. Click Add this calendar.
5. Open Google Apps Script and log in as your target account.
6. Click New project to create the project for the script.
7. Click "Untitled project" at the top to give the project a name, such as "Copy calendar events", and click Rename.
8. Replace the pre-filled code in Code.gs with the contents of copyCalendarEvents.gs. Update the configuration appropriately (see below).
9. Click the Save icon to save the project.
10. Next to "Services" click + to add a service.
11. Select "Google Calendar API" and click Add.
12. Click Deploy, then New deployment.
13. Click the cog next to "Select type" and choose "Web app".
14. For "Execute as", select "User accessing the web app".
15. Click Deploy.
16. In the left navigation, click "Triggers", then click Add Trigger.
17. Set the following options:
    • Function to run: copyAll
    • Event source: from calendar
    • Calendar owner email: your source calendar email
18. Click Save. Sign in as your target email address to allow the script. (You may need to allow popups)
19. Click Save again.
20. Back in the Editor, you can select to run the function "copyAll" from the menu to test the sync.

Configuration

The script begins with a config object taking the following options:

Parameter	Value	Description
<source_calendar>	string	Email address of the source calendar. The target calendar must be permitted to view this calendar.
<source_calendar>.prefix	string	A prefix for the event titles. If the prefix is Prefix, the title is prefixed with [Prefix] . Defaults to empty string, which adds no prefix to the title.
<source_calendar>.color	integer	One of the EventColor enum values. Defaults to 0, which does not change the event's colour.
<source_calendar>.visibility	string	One of "default", "public" or "private". Overrides the source calendar event's visibility, for instance to hide sensitive information. Defaults to the event's existing visibility.
<source_calendar>.syncDays	integer	How many days ahead to sync calendar events. Defaults to 14.