将日期格式从mm / dd / yy更改为dd / mm / yy

Question

I'm using a Google Form to collect dates from users, they use a datepicker. The format is US with mm/dd/yy (1/25/2016), but i need EU format dd/mm/yy (25/1/2016).

The script collects serval dates:

  var Date1 = e.values[24]; 
  var Date2 = e.values[25];
  var Date3 = e.values[26];
  var Date4 = e.values[27];  
  var Date5 = e.values[28];

How can i convert these to EU dateformat?

This is what iv'e tried so far without success:

1)

  function myFunction() {
      var preDate = "1/25/2016";
      var postDate = preDate.Utilities.formatDate(dt, "PST", "dd/mm/yy");
      Logger.log(postDate);
    }

Error: TypeError: Cannot call method "formatDate" of undefined.

2)

function myFunction() {
  var preDate = "1/25/2016"; 
  var postDate = Date.parseExact(preDate ,"dd/MM/yyyy")
  Logger.log(postDate);
}

Error: TypeError: Cannot find function parseExact in object function Date() { [native code for Date.Date, arity=1] }

Answer 1

If you have the dates in a Google Spreadsheet, you can use the Utilities.formatDate method to convert dates into another format.

function convertDate() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var source = sheet.getRange("A1").getValue();
  if (typeof source === "date") {
   sheet.getRange("B1").setValue(Utilities.formatDate(dt, "PST", "dd/mm/yy"));
  }
}

An easier option would be that you select the entire column in the spreadsheet and the change the default format under the Format menu (see screenshot).

Answer 2

You can use DateJS for that, like this:

http://code.google.com/p/datejs/wiki/APIDocumentation#parseExact

Date.parseExact("10/15/2004", "M/d/yyyy");  // The Date of 15-Oct-2004
Date.parse("15-Oct-2004", "d-MMM-yyyy");    // The Date of 15-Oct-2004
Date.parse("2004.10.15", "yyyy.MM.dd");     // The Date of 15-Oct-2004
Date.parseExact("10/15/2004", ["M/d/yyyy", "MMMM d, yyyy"]); // The Date of 15-Oct-2004

In your question you need that:

Date.parseExact("dateyouneed" ,"dd/MM/yyyy")