CalendarAppFull.gs

//get events from calendar
function getEvents() {
 
  var calenDar = CalendarApp.getCalendarById("Your Calendar ID");
  var lastDateOfYear = new Date(new Date().getFullYear(), 11, 31); // JavaScript counts months from 0 to 11. January is 0. December is 11.
  var events = calenDar.getEvents(new Date(), lastDateOfYear); // new Date() = today
  var spreadSheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  
  var lastRow = spreadSheet.getLastRow();
  spreadSheet.getRange(2, 1, lastRow, 5).clearContent();
  
  for(var i = 0; i < events.length; i++) {
    var title = events[i].getTitle();
    var start = events[i].getStartTime();
    var end = events[i].getEndTime();
    var location = events[i].getLocation();
    var description = events[i].getDescription();
    
    spreadSheet.getRange(i+2, 1).setValue(title);
    spreadSheet.getRange(i+2, 2).setValue(start);
    spreadSheet.getRange(i+2, 2).setNumberFormat("dd/mm/yyyy h:mm:ss");
    spreadSheet.getRange(i+2, 3).setValue(end);
    spreadSheet.getRange(i+2, 3).setNumberFormat("dd/mm/yyyy h:mm:ss");
    spreadSheet.getRange(i+2, 4).setValue(location);
    spreadSheet.getRange(i+2, 5).setValue(description);
  }
}


//delete and add events to calendar
function addEvents() {
  
  //open the event calendar
  var calenDar = CalendarApp.getCalendarById("Your Calendar ID");
  var spreadSheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  
  //pull information into the code, in a form that the code can understand
  var lastRow = spreadSheet.getLastRow();
  var data = spreadSheet.getRange("A2:E" + lastRow).getValues();
  
  /**
  [
    [event-1, start time-1, end time-1, location-1, description-1],
    [event-2, start time-2, end time-2, location-2, description-2],
    ..............................................................,
    [event-n, start time-n, end time-n, location-n, description-n]
  ]
  **/
  
  //delete events
  var lastDateOfYear = new Date(new Date().getFullYear(), 11, 31); // JavaScript counts months from 0 to 11. January is 0. December is 11.
  var events = calenDar.getEvents(new Date(), lastDateOfYear); // new Date() = today
  for (var i = 0; i < events.length; i++) {
    var eventsDelete = events[i];
    eventsDelete.deleteEvent();
    Utilities.sleep(100);
  }
  
  //add events
  for(var i = 0; i < data.length; i++) {
    var title = data[i][0];
    var startTime = data[i][1];
    Logger.log(startTime);
    var endTime = data[i][2];
    var location = data[i][3];
    var description = data[i][4];
    
    calenDar.createEvent(title, startTime, endTime, {location: location, description: description}); //(Title, Start Time, End Time, {options})
    //calenDar.createEvent(data[i][0], data[i][1], data[i][2], {location: data[i][3], description: data[i][4]}); //(Title, Start Time, End Time, {options})
    Utilities.sleep(100);
  }
}


//create menu for sync to calendar
function onOpen() {
  var ui = SpreadsheetApp.getUi();
  ui.createMenu('Sync to Calendar')
    .addItem('Add events to calendar', 'addEvents')
    .addItem('Get events from calendar', 'getEvents')
    .addToUi();
}