Outlook desktop to Google calendar

Outlook.vbs

Public WithEvents myOlFolder As Outlook.Folder
Public WithEvents myOlItems As Outlook.Items

Public Sub Application_Startup()
    Set myOlFolder = Application.GetNamespace("MAPI").GetDefaultFolder(olFolderCalendar)
    Set myOlItems = myOlFolder.Items
End Sub

Private Sub sendREST(ByVal Item As Object, ByVal Mode As String)
    Dim params As Object
    Set params = CreateObject("Scripting.Dictionary")
    params.Add "mode", Mode
    params.Add "subject", Item.Subject
    params.Add "start", Item.Start
    params.Add "end", Item.End
    params.Add "id", Item.GlobalAppointmentID
    Debug.Print JsonConverter.ConvertToJson(params, " ", 2)

    Dim httpObj As Object
    Set httpObj = CreateObject("MSXML2.ServerXMLHTTP")
    httpObj.Open "POST", "https://script.google.com/macros/******/exec", False
    httpObj.SetRequestHeader "Content-Type", "application/json"
    httpObj.Send JsonConverter.ConvertToJson(params)
    Debug.Print httpObj.responseText
    Set httpObj = Nothing
End Sub

Private Sub myOlFolder_BeforeItemMove(ByVal Item As Object, ByVal MoveTo As Folder, Cancel As Boolean)
    Dim delFolder As Folder
    Set delFolder = Application.GetNamespace("MAPI").GetDefaultFolder(olFolderDeletedItems)
    If MoveTo Is Nothing Then
        Call sendREST(Item, "delete")
    ElseIf delFolder = MoveTo Then
        Call sendREST(Item, "delete")
    End If
End Sub

Private Sub myOlItems_ItemAdd(ByVal Item As Object)
    Call sendREST(Item, "add")
End Sub

Private Sub myOlItems_ItemChange(ByVal Item As Object)
    Call sendREST(Item, "change")
End Sub

update_calendar.gs

function push_event(str) {

  let json = JSON.parse(str);

  let timeZone = Session.getScriptTimeZone();
  let t_start = new Date(json.start), t_end = new Date(json.end);
  if((t_end - t_start) % (24 * 60 * 60000) == 0){
    t_end = new Date(t_end.valueOf() - 1E3);
  }
  console.log(json);
  
  let lock = LockService.getScriptLock();
  if(!lock.tryLock(30E3)){return;}

  try{
    const calendar = CalendarApp.getCalendarById("******@gmail.com");
    let events = calendar.getEvents(
        new Date(t_start.valueOf() - 24 * 60 * 60E3 * 180), 
        new Date(t_end.valueOf() + 24 * 60 * 60E3 * 180),
        {search: json.id});
    
    let count_goal = ((json.mode == "delete") ? 0 : 1),
        count = 0;
    events.filter(function(event){
      if(count >= count_goal){return true;}
      event.setTitle(json.subject);
      event.setTime(t_start, t_end);
      count += 1;
      return false;
    }).forEach(function(event){
      event.deleteEvent();
    });
    
    while(count < count_goal){
      calendar.createEvent(
          json.subject, 
          t_start, t_end, 
          {description: `Copied from your Office 365 calendar( ${json.id} )`});
      count += 1;
    }
  }finally{
    lock.releaseLock();
  }
}

function test() {
  let str = `{
   "subject": "test",
   "start": "2021-05-18T20:00:00.000Z",
   "end": "2021-05-18T22:00:00.000Z",
   "id": "Outlook_id",
   "mode": "add"
  }`;
  push_event(str);
}

function doPost(e) {
  if (e == null || e.postData == null || e.postData.contents == null) {
    return;
  }
  push_event(e.postData.contents);
}