Determine correct date format of Google Form response - date

Question

What is the best way to determine the correct date format (dd/mm or mm/dd) of a Google Form response.
When I use the namedValues object:
function onFormSubmit(e){
var namedValues = e.namedValues;
var date = namedValues['Date']; // Date=[05/06/2018]
var date = new Date(date);
Logger.log(date); //Sun May 06 00:00:00 GMT+10:00 2018
}
When I use the value from the spreadsheet:
function onFormSubmit(e){
var range = e.range;
var row = range.getRow();
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName('Form Responses 1');
var date = sheet.getRange(row,2).getValue();
Logger.log(date); //Mon Jun 05 00:00:00 GMT+10:00 2018
}
I don't know whether I should be, but I am hesitant using the values from the spreadsheet in an onFormSubmit trigger, since I have experienced instability in the past where I think the trigger was running before the data was being posted to the spreadsheet.
I cannot find anything in the Google Forms documentation stating whether a date response is always in a consistent format. If it was always dd/mm/yyyy I could construct the date using the string parts.
Is there a way to use determine the correct date format from the namedValues object?
P.S I would rather not use the moment.js library for this one requirement, so keen to understand if its possible without.

Answer 1

You Google form will constantly submit the date in the same format, but your sheet might change the appearance of formatting.
Also, there is now a date format utility built into Apps script. You can change the date string to the format that you need.
// This formats the date as Greenwich Mean Time in the format
// year-month-dateThour-minute-second.
var formattedDate = Utilities.formatDate(new Date(), "GMT", "yyyy-MM-dd'T'HH:mm:ss'Z'");
Logger.log(formattedDate);