How to create chain events from one event on Google Calendar?

Question

I'm working for a non-profit and they want me to schedule their google calendar in such a way that once you create one event, let's say event A, it should automatically create events B,C,D and E.

For example- If I create an event "Anne's birthday", then the calendar should automatically create events (or sub-events) like Birthday plan meeting 1 week before the due date as event "B", Cake order 4 days before the due date as event "C", Party prep Shopping 2 days before as event "D" and Contacting invitees 1 day before as event "E" at specified dates and times before the due date and should be applicable for all similar future events.

score 2 · Answer 1 · answered Sep 30 '19 at 14:58

You should create a trigger event in your script that will fire your function when a new event is added to your calendar.

In order to do that, you have to synchronize your script to your calendar. You can follow these steps:

Create a script and enable the Calendar advance service.
Get your nextSyncToken for the calendar you want to track created events from, using Events.list() (run this function at the beginning, only once):

function initialSync() {
  var nextSyncToken = Calendar.Events.list('your_calendar_id')["nextSyncToken"];
  var sheet = SpreadsheetApp.getActive().getSheetByName('Sheet1');
  sheet.getRange('A1').setValue(nextSyncToken)
}

You have to store this nextSyncToken somewhere. I have used a spreadsheet for that in this sample, but you can use a database or whatever suits you (actually a spreadsheet is not the most secure way to store data, so I'd recommend using something else).

Create a trigger event that will fire whenever you update an event in your calendar (create, edit or delete an event). Also run this function only once, you only need a trigger:

function createTrigger() {
    var t = ScriptApp.newTrigger("createSubevents")
         .forUserCalendar("your_calendar_id")
         .onEventUpdated()
         .create();
}

Create function that will create 'subevents' every time a new event is created. This function should have the same name as the one you invoke in the trigger you just created. In the following function, only a 'subevent' is created, repeat the process or create a function to do the same for how many subevents you want to create (you should run this function at least once to get all needed permissions):

function createSubevents() {
  // Getting current syncToken from spreadsheet
  var params = {
    syncToken: sheet.getRange('A1').getValue()
  }
  // Retrieve events that were updated since last call
  var events = Calendar.Events.list('your_calendar_id', params);
  var items = events["items"];
  // Update sync token in spreadsheet
  sheet.getRange('A1').setValue(events["nextSyncToken"]);
  // Loop through updated items (in this case, it should only be one)
  for(var i = 0; i < items.length; i++) {
    var item = items[i];
    var mainStartTime = new Date(item.start.date);
    var mainEndTime = new Date(item.end.date);
    var dateCreated = new Date(item.created);
    var dateUpdated = new Date(item.updated);
    // Check if updated event was created (not deleted nor merely edited)
    if (dateUpdated - dateCreated < 1000 && item.status != "cancelled") {
      var mainEventTitle = item.summary;
      // Setting event B title
      var eventBTitle = 'whatever_event_B_is_for ' + mainEventTitle;
      // Setting event B dates
      var numDaysB = 7 // Number of days before main event, edit according to each event
      var startTimeB = mainStartTime;
      startTimeB.setDate(mainStartTime.getDate() - numDaysB);
      var endTimeB = mainEndTime;
      endTimeA.setDate(mainEndTime.getDate() - numDaysB);
      // Creating event B
      createEvent(eventBTitle, startTimeB, endTimeB)
    }
  }
}

// This function receives a title, a start time and an end time and creates the corresponding event
function createEvent(title, startTime, endTime) {
  try {
    var calendar = CalendarApp.getCalendarById('your_calendar_id');
    var event = calendar.createEvent(title, startTime, endTime)
    Logger.log(event)
  } catch(err) {
    Logger.log(err)
  }
}

I hope this is useful to you!

How to create chain events from one event on Google Calendar?

1 Answers1