How to check if a string is a legal “dd/mm/yyyy” date?

Question

Given a string str, how could I check if it is in the dd/mm/yyyy format and contains a legal date ?

Some examples:

bla bla          


        

Answer 1

I'm going to answer a different question, as Misha Moroshko's has already been well-answered: use HTML5. That is, on the assumption that the strings in question arise as user inputs through a Web browser, I propose that the entries be received as

   <input type = "date" ...

I recognize that not all browsers likely to be in use will interpret "date" in a way that rigorously enforces validity. It's the right thing to do, though, will certainly improve as time goes on, and might well be good enough in a particular context even now simply to eliminate the need to validate the date-string after the fact.

Answer 2

Edit: exact solution below

You could do something like this, but with a more accurate algorithm for day validation:

function testDate(str) {
  var t = str.match(/^(\d{2})\/(\d{2})\/(\d{4})$/);
  if(t === null)
    return false;
  var d = +t[1], m = +t[2], y = +t[3];

  // Below should be a more acurate algorithm
  if(m >= 1 && m <= 12 && d >= 1 && d <= 31) {
    return true;  
  }

  return false;
}

http://jsfiddle.net/aMWtj/

Date validation alg.: http://www.eee.hiflyers.co.uk/ProgPrac/DateValidation-algorithm.pdf

Exact solution: function that returns a parsed date or null, depending exactly on your requirements.

function parseDate(str) {
  var t = str.match(/^(\d{2})\/(\d{2})\/(\d{4})$/);
  if(t !== null){
    var d = +t[1], m = +t[2], y = +t[3];
    var date = new Date(y, m - 1, d);
    if(date.getFullYear() === y && date.getMonth() === m - 1) {
      return date;   
    }
  }

  return null;
}

http://jsfiddle.net/aMWtj/2/

In case you need the function to return true/false and for a yyyy/mm/dd format

function IsValidDate(pText) {
    var isValid = false ;
    var t = pText.match(/^(\d{4})\/(\d{2})\/(\d{2})$/);

    if (t !== null) {
        var y = +t[1], m = +t[2], d = +t[3];
        var date = new Date(y, m - 1, d);

        isValid = (date.getFullYear() === y && date.getMonth() === m - 1) ;
    }

    return isValid ;
}

Answer 3

Personally, I think the best solution would be to modify the UI to use dropdowns for the month and possibly day selections.

Trying to figure out if 1/2/2001 is January 2nd or February 1st based solely on that input string is impossible.

Answer 4

for dd/mm/yyyy format only

^(0?[1-9]|[12][0-9]|3[01])[\/](0?[1-9]|1[012])[\/]\d{4}$

Answer 5

Recent discovery: You can use date.js lib, it adds function Date.parseExact so you can just do Date.parseExact(dateString,"dd/MM/yyyy"). It fails when month is 00, but its still usefull.

Answer 6

you can use regular exp to validate date . try like this :

  re = /^\d{1,2}\/\d{1,2}\/\d{4}$/; 
if(form.mydate.value != '' && !form.mydate.value.match(re))
  //do something here

note: this will only work for dd/mm/yyyy

for exact match of your requirement use

 re = /^\d{2}\/\d{2}\/\d{4}$/;