Advanced Calendar Service

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The advanced Calendar service allows you to use the public Google Calendar API in Apps Script. Much like Apps Script's built-in Calendar service, this API allows scripts to access and modify the user's Google Calendar, including additional calendars that the user is subscribed to. In most cases, the built-in service is easier to use, but this advanced service provides a few extra features, including setting the background color for individual events.

Reference

For detailed information on this service, see the reference documentation for the public Google Calendar API. Like all advanced services in Apps Script, the advanced Calendar service uses the same objects, methods, and parameters as the public API. For more information, see How method signatures are determined.

To report issues and find other support, see the Calendar support guide.

HTTP request headers

The advanced Calendar service can accept the HTTP request headers If-Match and If-None-Match. For details, see the reference documentation.

Sample code

The sample code below uses version 3 of the API.

Creating events

The following example demonstrates how to create an event in the user's default calendar.

advanced/calendar.gs
/**
 * Creates an event in the user's default calendar.
 * @see https://developers.google.com/calendar/api/v3/reference/events/insert
 */
function createEvent() {
  const calendarId = 'primary';
  const start = getRelativeDate(1, 12);
  const end = getRelativeDate(1, 13);
  // event details for creating event.
  let event = {
    summary: 'Lunch Meeting',
    location: 'The Deli',
    description: 'To discuss our plans for the presentation next week.',
    start: {
      dateTime: start.toISOString()
    },
    end: {
      dateTime: end.toISOString()
    },
    attendees: [
      {email: 'gduser1@workspacesample.dev'},
      {email: 'gduser2@workspacesample.dev'}
    ],
    // Red background. Use Calendar.Colors.get() for the full list.
    colorId: 11
  };
  try {
    // call method to insert/create new event in provided calandar
    event = Calendar.Events.insert(event, calendarId);
    Logger.log('Event ID: ' + event.id);
  } catch (err) {
    Logger.log('Failed with error %s', err.message);
  }
}

/**
 * Helper function to get a new Date object relative to the current date.
 * @param {number} daysOffset The number of days in the future for the new date.
 * @param {number} hour The hour of the day for the new date, in the time zone
 *     of the script.
 * @return {Date} The new date.
 */
function getRelativeDate(daysOffset, hour) {
  const date = new Date();
  date.setDate(date.getDate() + daysOffset);
  date.setHours(hour);
  date.setMinutes(0);
  date.setSeconds(0);
  date.setMilliseconds(0);
  return date;
}

Listing calendars

The following example demonstrates how to retrieve details about the calendars shown in the user's calendar list.

advanced/calendar.gs
/**
 * Lists the calendars shown in the user's calendar list.
 * @see https://developers.google.com/calendar/api/v3/reference/calendarList/list
 */
function listCalendars() {
  let calendars;
  let pageToken;
  do {
    calendars = Calendar.CalendarList.list({
      maxResults: 100,
      pageToken: pageToken

    });
    if (!calendars.items || calendars.items.length === 0) {
      Logger.log('No calendars found.');
      return;
    }
    // Print the calendar id and calendar summary
    for (const calendar of calendars.items) {
      Logger.log('%s (ID: %s)', calendar.summary, calendar.id);
    }
    pageToken = calendars.nextPageToken;
  } while (pageToken);
}

Listing events

The following example demonstrates how to list the next 10 upcoming events in the user's default calendar.

advanced/calendar.gs
/**
 * Lists the next 10 upcoming events in the user's default calendar.
 * @see https://developers.google.com/calendar/api/v3/reference/events/list
 */
function listNext10Events() {
  const calendarId = 'primary';
  const now = new Date();
  const events = Calendar.Events.list(calendarId, {
    timeMin: now.toISOString(),
    singleEvents: true,
    orderBy: 'startTime',
    maxResults: 10
  });
  if (!events.items || events.items.length === 0) {
    Logger.log('No events found.');
    return;
  }
  for (const event of events.items) {
    if (event.start.date) {
      // All-day event.
      const start = new Date(event.start.date);
      Logger.log('%s (%s)', event.summary, start.toLocaleDateString());
      return;
    }
    const start = new Date(event.start.dateTime);
    Logger.log('%s (%s)', event.summary, start.toLocaleString());
  }
}

Conditionally modifying an event

The following example shows how to conditionally update a Calendar event using the If-Match header. The script creates a new event, waits 30 seconds, then updates the event only if no event details have changed since the event was created.

advanced/calendar.gs
/**
 * Creates an event in the user's default calendar, waits 30 seconds, then
 * attempts to update the event's location, on the condition that the event
 * has not been changed since it was created.  If the event is changed during
 * the 30-second wait, then the subsequent update will throw a 'Precondition
 * Failed' error.
 *
 * The conditional update is accomplished by setting the 'If-Match' header
 * to the etag of the new event when it was created.
 */
function conditionalUpdate() {
  const calendarId = 'primary';
  const start = getRelativeDate(1, 12);
  const end = getRelativeDate(1, 13);
  let event = {
    summary: 'Lunch Meeting',
    location: 'The Deli',
    description: 'To discuss our plans for the presentation next week.',
    start: {
      dateTime: start.toISOString()
    },
    end: {
      dateTime: end.toISOString()
    },
    attendees: [
      {email: 'gduser1@workspacesample.dev'},
      {email: 'gduser2@workspacesample.dev'}
    ],
    // Red background. Use Calendar.Colors.get() for the full list.
    colorId: 11
  };
  event = Calendar.Events.insert(event, calendarId);
  Logger.log('Event ID: ' + event.getId());
  // Wait 30 seconds to see if the event has been updated outside this script.
  Utilities.sleep(30 * 1000);
  // Try to update the event, on the condition that the event state has not
  // changed since the event was created.
  event.location = 'The Coffee Shop';
  try {
    event = Calendar.Events.update(
        event,
        calendarId,
        event.id,
        {},
        {'If-Match': event.etag}
    );
    Logger.log('Successfully updated event: ' + event.id);
  } catch (e) {
    Logger.log('Fetch threw an exception: ' + e);
  }
}

Conditionally retrieving an event

The following example shows how to conditionally fetch a Calendar event using the If-None-Match header. The script creates a new event, then polls the event for changes for 30 seconds. Any time the event changes, the new version is fetched.

advanced/calendar.gs
/**
 * Creates an event in the user's default calendar, then re-fetches the event
 * every second, on the condition that the event has changed since the last
 * fetch.
 *
 * The conditional fetch is accomplished by setting the 'If-None-Match' header
 * to the etag of the last known state of the event.
 */
function conditionalFetch() {
  const calendarId = 'primary';
  const start = getRelativeDate(1, 12);
  const end = getRelativeDate(1, 13);
  let event = {
    summary: 'Lunch Meeting',
    location: 'The Deli',
    description: 'To discuss our plans for the presentation next week.',
    start: {
      dateTime: start.toISOString()
    },
    end: {
      dateTime: end.toISOString()
    },
    attendees: [
      {email: 'gduser1@workspacesample.dev'},
      {email: 'gduser2@workspacesample.dev'}
    ],
    // Red background. Use Calendar.Colors.get() for the full list.
    colorId: 11
  };
  try {
    // insert event
    event = Calendar.Events.insert(event, calendarId);
    Logger.log('Event ID: ' + event.getId());
    // Re-fetch the event each second, but only get a result if it has changed.
    for (let i = 0; i < 30; i++) {
      Utilities.sleep(1000);
      event = Calendar.Events.get(calendarId, event.id, {}, {'If-None-Match': event.etag});
      Logger.log('New event description: ' + event.start.dateTime);
    }
  } catch (e) {
    Logger.log('Fetch threw an exception: ' + e);
  }
}

Synchronizing events

The following example demonstrates how to retrieve events using sync tokens. When you include a sync token in a Calendar advanced service request, the resulting response only includes items that have changed since that token was generated, enabling more efficient processing. See Synchronize Resources Efficiently for more details on the syncing process.

The following example makes use of the same getRelativeDate(daysOffset, hour) method defined in the above examples.

advanced/calendar.gs
/**
 * Retrieve and log events from the given calendar that have been modified
 * since the last sync. If the sync token is missing or invalid, log all
 * events from up to a month ago (a full sync).
 *
 * @param {string} calendarId The ID of the calender to retrieve events from.
 * @param {boolean} fullSync If true, throw out any existing sync token and
 *        perform a full sync; if false, use the existing sync token if possible.
 */
function logSyncedEvents(calendarId, fullSync) {
  const properties = PropertiesService.getUserProperties();
  const options = {
    maxResults: 100
  };
  const syncToken = properties.getProperty('syncToken');
  if (syncToken && !fullSync) {
    options.syncToken = syncToken;
  } else {
    // Sync events up to thirty days in the past.
    options.timeMin = getRelativeDate(-30, 0).toISOString();
  }
  // Retrieve events one page at a time.
  let events;
  let pageToken;
  do {
    try {
      options.pageToken = pageToken;
      events = Calendar.Events.list(calendarId, options);
    } catch (e) {
      // Check to see if the sync token was invalidated by the server;
      // if so, perform a full sync instead.
      if (e.message === 'Sync token is no longer valid, a full sync is required.') {
        properties.deleteProperty('syncToken');
        logSyncedEvents(calendarId, true);
        return;
      }
      throw new Error(e.message);
    }
    if (events.items && events.items.length === 0) {
      Logger.log('No events found.');
      return;
    }
    for (const event of events.items) {
      if (event.status === 'cancelled') {
        Logger.log('Event id %s was cancelled.', event.id);
        return;
      }
      if (event.start.date) {
        const start = new Date(event.start.date);
        Logger.log('%s (%s)', event.summary, start.toLocaleDateString());
        return;
      }
      // Events that don't last all day; they have defined start times.
      const start = new Date(event.start.dateTime);
      Logger.log('%s (%s)', event.summary, start.toLocaleString());
    }
    pageToken = events.nextPageToken;
  } while (pageToken);
  properties.setProperty('syncToken', events.nextSyncToken);
}