There is something else I just noticed I may need some help with. I would also like for it to be able to update any edits I made to the spreadsheet but also not duplicate the events that were already made from the first run. I know it's got something to do with the GetID string but I'm not too sure how to go about it since this is my first time coding, would really appreciate if anyone can aid with that too? :'D

The following is my code:

function addEvents(){
  var ss = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var lr = ss.getLastRow();
  var cal = CalendarApp.getCalendarById("CalendarID");

  var data = ss.getRange("A3:C" + lr).getValues();

  for(var i = 0; i<data.length; i++){
    cal.createAllDayEvent(data[i][1], data[i][0], {description: data[i][2]});

  }

}

In my Google Spreadsheet, the order of the data is as follows (data only appears in A3:C3 and downwards to the bottom rows): column A: Date, B: Event Title, C: Description