[javascript] Check if a string is a date value

What is an easy way to check if a value is a valid date, any known date format allowed.

For example I have the values 10-11-2009, 10/11/2009, 2009-11-10T07:00:00+0000 which should all be recognized as date values, and the values 200, 10, 350, which should not be recognized as a date value. What is the simplest way to check this, if this is even possible? Because timestamps would also be allowed.

Try this:

if (var date = new Date(yourDateString)) {
    // if you get here then you have a valid date       
}

None of the answers here address checking whether the date is invalid such as February 31. This function addresses that by checking if the returned month is equivalent to the original month and making sure a valid year was presented.

//expected input dd/mm/yyyy or dd.mm.yyyy or dd-mm-yyyy
function isValidDate(s) {
  var separators = ['\\.', '\\-', '\\/'];
  var bits = s.split(new RegExp(separators.join('|'), 'g'));
  var d = new Date(bits[2], bits[1] - 1, bits[0]);
  return d.getFullYear() == bits[2] && d.getMonth() + 1 == bits[1];
} 

new Date(date) === 'Invalid Date' only works in Firefox and Chrome. IE8 (the one I have on my machine for testing purposes) gives NaN.

As was stated to the accepted answer, Date.parse(date) will also work for numbers. So to get around that, you could also check that it is not a number (if that's something you want to confirm).

var parsedDate = Date.parse(date);

// You want to check again for !isNaN(parsedDate) here because Dates can be converted
// to numbers, but a failed Date parse will not.
if (isNaN(date) && !isNaN(parsedDate)) {
    /* do your work */
}

function isDate(dateStr) {
  return !isNaN(new Date(dateStr).getDate());
}

• This will work on any browser since it does not rely on "Invalid Date" check.
• This will work with legacy code before ES6.
• This will work without any library.
• This will work regardless of any date format.
• This does not rely on Date.parse which fails the purpose when values like "Spiderman 22" are in date string.
• This does not ask us to write any RegEx.

By referring to all of the above comments, I have come to a solution.

This works if the Date passed is in ISO format or need to manipulate for other formats.

var isISO = "2018-08-01T18:30:00.000Z";

if (new Date(isISO) !== "Invalid Date" && !isNaN(new Date(isISO))) {
    if(isISO == new Date(isISO).toISOString()) {
        console.log("Valid date");
    } else {
        console.log("Invalid date");
    }
} else {
    console.log("Invalid date");
}

You can play here on JSFiddle.

Here is an improved function that uses only Date.parse():

function isDate(s) {
    if(isNaN(s) && !isNaN(Date.parse(s)))
        return true;
    else return false;
}

Note: Date.parse() will parse numbers: for example Date.parse(1) will return a date. So here we check if s is not a number the, if it is a date.

Ok, this is an old question, but I found another solution while checking the solutions here. For me works to check if the function getTime() is present at the date object:

const checkDate = new Date(dateString);

if (typeof checkDate.getTime !== 'function') {
  return;
}

I would do this

var myDateStr= new Date("2015/5/2");

if( ! isNaN ( myDateStr.getMonth() )) {
    console.log("Valid date");
}
else {
    console.log("Invalid date");
}

Play here

document.getElementById('r1').innerHTML = dayjs('sdsdsd').isValid()_x000D_
_x000D_
document.getElementById('r2').innerHTML = dayjs('2/6/20').isValid()

<script src="https://unpkg.com/[email protected]/dayjs.min.js"></script>_x000D_
_x000D_
<p>'sdsdsd' is a date: <span id="r1"></span></p>_x000D_
<p>'2/6/20' is a date: <span id="r2"></span></p>

A light weight library is ready for you: Day.js

2015 Update

It is an old question but other new questions like:

• How to validate if a string is a valid date in js

get closed as duplicates of this one, so I think it's important to add some fresh info here. I'm writing it because I got scared thinking that people actually copy and paste some of the code posted here and use it in production.

Most of the answers here either use some complex regular expressions that match only some very specific formats and actually do it incorrectly (like matching January 32nd while not matching actual ISO date as advertised - see demo) or they try to pass anything to the Date constructor and wish for the best.

Using Moment

As I explained in this answer there is currently a library available for that: Moment.js

It is a library to parse, validate, manipulate, and display dates in JavaScript, that has a much richer API than the standard JavaScript date handling functions.

It is 12kB minified/gzipped and works in Node.js and other places:

bower install moment --save # bower
npm install moment --save   # npm
Install-Package Moment.js   # NuGet
spm install moment --save   # spm
meteor add momentjs:moment  # meteor

Using Moment you can be very specific about checking valid dates. Sometimes it is very important to add some clues about the format that you expect. For example, a date such as 06/22/2015 looks like a valid date, unless you use a format DD/MM/YYYY in which case this date should be rejected as invalid. There are few ways how you can tell Moment what format you expect, for example:

moment("06/22/2015", "MM/DD/YYYY", true).isValid(); // true
moment("06/22/2015", "DD/MM/YYYY", true).isValid(); // false

The true argument is there so the Moment won't try to parse the input if it doesn't exactly conform to one of the formats provided (it should be a default behavior in my opinion).

You can use an internally provided format:

moment("2015-06-22T13:17:21+0000", moment.ISO_8601, true).isValid(); // true

And you can use multiple formats as an array:

var formats = [
    moment.ISO_8601,
    "MM/DD/YYYY  :)  HH*mm*ss"
];
moment("2015-06-22T13:17:21+0000", formats, true).isValid(); // true
moment("06/22/2015  :)  13*17*21", formats, true).isValid(); // true
moment("06/22/2015  :(  13*17*21", formats, true).isValid(); // false

See: DEMO.

Other libraries

If you don't want to use Moment.js, there are also other libraries:

• XDate
• DateJS

2016 Update

I created the immoment module that is like (a subset of) Moment but without surprises caused by mutation of existing objects (see the docs for more info).

2018 Update

Today I recommend using Luxon for date/time manipulation instead of Moment, which (unlike Moment) makes all object immutable so there are no nasty surprises related to implicit mutation of dates.

More info

See also:

• Managing Dates and Times Using Moment.js by Jay Raj
• Working with JavaScript Dates Using Moment.js by Bradley Holbrook

A series of articles by Rob Gravelle on JavaScript date parsing libraries:

• A Roundup of Popular JavaScript Date Parsing Libraries: Moment.js
• A Roundup of Popular JavaScript Date Parsing Libraries: Datejs
• A Roundup of Popular JavaScript Date Parsing Libraries: XDate

Bottom line

Of course anyone can try to reinvent the wheel, write a regular expression (but please actually read ISO 8601 and RFC 3339 before you do it) or call buit-in constructors with random data to parse error messages like 'Invalid Date' (Are you sure this message is exactly the same on all platforms? In all locales? In the future?) or you can use a tested solution and use your time to improve it, not reinvent it. All of the libraries listed here are open source, free software.

This callable function works perfectly, returns true for valid date. Be sure to call using a date on ISO format (yyyy-mm-dd or yyyy/mm/dd):

function validateDate(isoDate) {

    if (isNaN(Date.parse(isoDate))) {
        return false;
    } else {
        if (isoDate != (new Date(isoDate)).toISOString().substr(0,10)) {
            return false;
        }
    }
    return true;
}

This is how I solved this problem in an app I'm working on right now:

updated based on feedback from krillgar:

var isDate = function(date) {
    return (new Date(date) !== "Invalid Date") && !isNaN(new Date(date));
}

Use Regular expression to validate it.

isDate('2018-08-01T18:30:00.000Z');

isDate(_date){
        const _regExp  = new RegExp('^(-?(?:[1-9][0-9]*)?[0-9]{4})-(1[0-2]|0[1-9])-(3[01]|0[1-9]|[12][0-9])T(2[0-3]|[01][0-9]):([0-5][0-9]):([0-5][0-9])(.[0-9]+)?(Z)?$');
        return _regExp.test(_date);
    }

This is how I end up doing it. This will not cover all formats. You have to adjust accordingly. I have control on the format, so it works for me

function isValidDate(s) {
            var dt = "";
            var bits = [];
            if (s && s.length >= 6) {
                if (s.indexOf("/") > -1) {
                    bits = s.split("/");
                }
                else if (s.indexOf("-") > -1) {
                    bits = s.split("-");
                }
                else if (s.indexOf(".") > -1) {
                    bits = s.split(".");
                }
                try {
                    dt = new Date(bits[2], bits[0] - 1, bits[1]);
                } catch (e) {
                    return false;
                }
                return (dt.getMonth() + 1) === parseInt(bits[0]);
            } else {
                return false;
            }
        }

How about something like this? It will test if it is a Date object or a date string:

function isDate(value) {
    var dateFormat;
    if (toString.call(value) === '[object Date]') {
        return true;
    }
    if (typeof value.replace === 'function') {
        value.replace(/^\s+|\s+$/gm, '');
    }
    dateFormat = /(^\d{1,4}[\.|\\/|-]\d{1,2}[\.|\\/|-]\d{1,4})(\s*(?:0?[1-9]:[0-5]|1(?=[012])\d:[0-5])\d\s*[ap]m)?$/;
    return dateFormat.test(value);
}

I should mention that this doesn't test for ISO formatted strings but with a little more work to the RegExp you should be good.

Here's a minimalist version.

var isDate = function (date) {
    return!!(function(d){return(d!=='Invalid Date'&&!isNaN(d))})(new Date(date));
}

I know it's an old question but I faced the same problem and saw that none of the answers worked properly - specifically weeding out numbers (1,200,345,etc..) from dates, which is the original question. Here is a rather unorthodox method I could think of and it seems to work. Please point out if there are cases where it will fail.

if(sDate.toString() == parseInt(sDate).toString()) return false;

This is the line to weed out numbers. Thus, the entire function could look like:

function isDate(sDate) {  _x000D_
  if(sDate.toString() == parseInt(sDate).toString()) return false; _x000D_
  var tryDate = new Date(sDate);_x000D_
  return (tryDate && tryDate.toString() != "NaN" && tryDate != "Invalid Date");  _x000D_
}_x000D_
_x000D_
console.log("100", isDate(100));_x000D_
console.log("234", isDate("234"));_x000D_
console.log("hello", isDate("hello"));_x000D_
console.log("25 Feb 2018", isDate("25 Feb 2018"));_x000D_
console.log("2009-11-10T07:00:00+0000", isDate("2009-11-10T07:00:00+0000"));

SimpleDateFormat sdf = new SimpleDateFormat(dateFromat);
sdf.setLenient(false);

By default this is set to TRUE. So even strings of wrong format return good values.

I have used it something like this :

SimpleDateFormat formatter = new SimpleDateFormat("yyyy/MM/dd");
formatter.setLenient(false);
String value = "1990/13/23"; 

try {
      Date date = formatter.parse(value);
      System.out.println(date);
    }catch (ParseException e) 
  {
    System.out.println("its bad");
  }

is it fine to check for a Date related function is available for the object to find whether it is a Date object or not ?

like

var l = new Date();
var isDate = (l.getDate !== undefined) ? true; false;