Google Sheets to Googel Calendar - Duplications - google-apps-script

Question

I've been reading a few questions and help on managing a google sheet then transferring info to google calendar via email.
I'm using the below code which i pulled from various places and its working really well however a couple of things i'm struggling with:
every time i run the script it duplicates the events, how do i stop this from happening every time the script is run - but still allow for say, addition of new email addresses down the line or update the calendar entry?
cant quite get the starttime and endtime to work nicely - the script is run off a tab in a google sheet that pulls its data from another tab (data entry)to make life easier for my users; is there a trick to the format for yyyy-mm-dd-hh:mm:ss?
possible to setup a line of code as part of this to send out automatic reminders say 7 days out from the event?
Appreciate any and all help on this!
Code thats working right now:
function CreateEvent() {
var spreadsheet = SpreadsheetApp.getActiveSheet();
var calendarId = spreadsheet.getRange('***<LINKTOCELLTHATHASCALENDARID>***').getValue();
var eventCal = CalendarApp.getCalendarById('***CALENDARID<DELETED>***');
var lr = spreadsheet.getLastRow();
Logger.log(lr);
var count = spreadsheet.getRange("A2:F"+lr+"").getValues();
for (x=0; x<count.length; x++) {
var shift = count[x];
var title = shift[0];
var startTime = shift[1];
var endTime = shift[2];
var guests = shift[3];
var description = shift[4];
var location = shift[5];
var event = {
'location': location,
'description': description,
'guests':guests +',',
'sendInvites': 'True',
}
eventCal.createEvent(title, startTime, endTime, event)
}
}

Answer 1

function CreateEvent() {
var sh=SpreadsheetApp.getActiveSheet();
var calendarId=sh.getRange('***<LINKTOCELLTHATHASCALENDARID>***').getValue();
var eventCal=CalendarApp.getCalendarById('***CALENDARID<DELETED>***');
var drg=sh.getRange(2,1,sh.getLastRow()-1,7);
var dA=drg.getValues();
var crg=sh.getRange(2,7,sh.getLastRow()-1,1);//save that event was created in column G
var cA=crg.getValues();
for (i=0;i<dA.length;i++) {
var shift=dA[i];
var title=shift[0];
var startTime=shift[1];
var endTime=shift[2];
var guests=shift[3];
var description=shift[4];
var location=shift[5];
if(!shift[6]) {
var event={'location': location,'description': description,'guests':guests +',','sendInvites': 'True'}
eventCal.createEvent(title, startTime, endTime, event)
cA[i][0]="CREATED";//keeps this event from being created again
}
}
crg.setValues(cA);
}