Check if date is a valid one

Question

Following is the scenario:

I have a String date and a date format which is different. Ex.:
date: 2016-10-19
dateFormat: "DD-MM-YYYY".

I need to check if this date is a valid date.

I have tried following things

var d = moment("2016-10-19",dateFormat);

d.isValid() is returning false every time. Does not Moment.js parse the date in the given format?

Then I tried to format the date in DD-MM-YYYY first and then pass it to Moment.js:

var d = moment("2016-10-19").format(dateFormat);
var date = moment(d, dateFormat);

Now date.isValid() is giving me the desired result, but here the Moment.js date object is created twice. How can I avoid this? Is there a better solution?

FYI I am not allowed to change the dateFormat.

Are you not allowed to change the value of dateFormat? In that case, you will have to change the format of the input, since 2016-10-19 is YYYY-MM-DD, not DD-MM-YYYY. What are you allowed to change? — Pochen, Oct 19 '16 at 06:38
The input is coming from date picker. Can't change that too :( — Ganesh, Oct 19 '16 at 06:41
May I ask why you are not allowed to change the dateFormat variable? var d = moment("19-10-2016", "DD-MM-YYYY"); would solve your problems as far as I'm concerned — Pochen, Oct 19 '16 at 06:43
really can't say. But that is not in my control to change that value. — Ganesh, Oct 19 '16 at 06:44
Possible duplicate of [How to test a string is valid date or not using moment?](http://stackoverflow.com/questions/28227862/how-to-test-a-string-is-valid-date-or-not-using-moment) — Luca Fagioli, May 11 '17 at 15:39

score 272 · Accepted Answer · answered Oct 19 '16 at 12:35

272

Was able to find the solution. Since the date I am getting is in ISO format, only providing date to moment will validate it, no need to pass the dateFormat.

var date = moment("2016-10-19");

And then date.isValid() gives desired result.

answered Oct 19 '16 at 12:35

Ganesh

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Does anyone know what the current preferred method is now? This method now throws the following "Deprecation Warning": moment construction falls back to js Date. This is discouraged and will be removed in upcoming major release. Please refer to https://github.com/moment/moment/issues/1407 for more info. – Andrew Sep 07 '18 at 23:53
1

@Andrew Please look at https://stackoverflow.com/questions/23263380/deprecation-warning-moment-construction-falls-back-to-js-date, https://github.com/moment/moment/issues/2535 – Ganesh Sep 10 '18 at 05:27
11

Just a heads up that this doesn't always work: `var a = moment('12345'); a.isValid() // is true` This fails because moment will fall back to the default date object if it can't parse the date. And the default date object will always return a date (just not the one you want.) – Mauvis Ledford Oct 24 '18 at 22:50
That Github thread, the first comments outlines why it's deprecated but doesn't provide an alternative for checking invalid dates. When using `moment('1234').isValid()` as documented it still throws a deprecation notice. – png Nov 21 '18 at 21:31
5

need to add that `moment('02').isValid() === true`, so you might want to be careful with that – Bruno Finger Dec 03 '18 at 13:53
4

Also `moment('abcde 1').isValid() === true` – Amiram Korach Jan 02 '19 at 09:08
Warning: isValid() is not in any way reliable without a format. Do not be burnt – zanderwar Jun 26 '19 at 04:21
5

This is a wrong answer because I always get true whatever string I pass in – Billal Begueradj Jan 24 '20 at 08:06
var date = moment("2016-10-32") this is not valid date but it is returning date is valid – dev verma Jul 28 '20 at 09:51
Also `moment(undefined).isValid() === true` (?) – Pablo Lammel Aug 19 '22 at 14:37

score 163 · Answer 2 · answered Dec 08 '17 at 17:39

163

var date = moment('2016-10-19', 'DD-MM-YYYY', true);

You should add a third argument when invoking moment that enforces strict parsing. Here is the relevant portion of the moment documentation http://momentjs.com/docs/#/parsing/string-format/ It is near the end of the section.

answered Dec 08 '17 at 17:39

Andrew

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This has no effect. – Billal Begueradj Jan 24 '20 at 08:32
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this answer should be the correct answer........@Begueradj this has effect, try using different values, sometimes correct and sometimes wrong – Akki Feb 21 '20 at 09:48
1

And you can read about strict parsing [here](https://momentjs.com/guides/#/parsing/strict-mode/) – kuhr Mar 11 '20 at 13:12
1

This will let you enter 0000 as a year – eddy Jun 19 '20 at 14:34

score 47 · Answer 3 · answered Jul 09 '19 at 04:35

47

I just found a really messed up case.

moment('Decimal128', 'YYYY-MM-DD').isValid() // true

answered Jul 09 '19 at 04:35

Sam Araiza

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`moment('Decimal128', 'YYYY-MM-DD', true).isValid() // false`. Use strict mode :) https://momentjs.com/guides/#/parsing/strict-mode/ – jklemmack Nov 25 '19 at 20:30
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Strict mode works. Weird that this has to be strict though. – Sam Araiza Oct 07 '20 at 19:24

tim-montague · Answer 4 · 2021-12-16T06:41:45.460

How to check if a string is a valid date using Moment, when the date and date format are different

Sorry, but did any of the given solutions on this thread actually answer the question that was asked?

I have a String date and a date format which is different. Ex.: date: 2016-10-19 dateFormat: "DD-MM-YYYY". I need to check if this date is a valid date.

The following works for me...

const date = '2016-10-19';
const dateFormat = 'DD-MM-YYYY';
const toDateFormat = moment(new Date(date)).format(dateFormat);
moment(toDateFormat, dateFormat, true).isValid();

// Note I: `new Date()` circumvents the warning that
//   Moment throws (https://momentjs.com/guides/#/warnings/js-date/),
//   but may not be optimal.

// Note II: passing `true` as third argument to `moment()` enables strict-mode
//   https://momentjs.com/guides/#/parsing/strict-mode/

But honestly, don't understand why moment.isDate()(as documented) only accepts an object. Should also support a string in my opinion.

if we pass true as 3rd argument for moment, it check's for exact date format. — Raj Kumar N, Oct 22 '19 at 10:48

gschambial · Answer 5 · 2016-10-19T08:22:31.987

22

Here you go: Working Fidddle

$(function(){
  var dateFormat = 'DD-MM-YYYY';
  alert(moment(moment("2012-10-19").format(dateFormat),dateFormat,true).isValid());
});

edited Oct 19 '16 at 08:22

answered Oct 19 '16 at 06:46

gschambial

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Like I said the dateFormat is 'DD-MM-YYYY' and I am not allowed to change it. – Ganesh Oct 19 '16 at 06:48
Oh i see. Let me see on that. – gschambial Oct 19 '16 at 06:49
Is it allowed to change the date string here `2016-10-19`? – gschambial Oct 19 '16 at 06:54
Nope. That is coming from date picker – Ganesh Oct 19 '16 at 06:55
4

Can't you modify it after it comes from datepicker and before you input it to `var d = moment("2016-10-19",dateFormat);`? – gschambial Oct 19 '16 at 06:56
That is what I did in the second solution that I mentioned in description but that results in creating two moment objects which I want to avoid. – Ganesh Oct 19 '16 at 06:58
@Ganesh You don't have to modify `dateFormat` or `dateString`. – gschambial Oct 19 '16 at 08:17
It outputs true but it should output false. Plus whatever I write, it gives random results – Billal Begueradj Jan 24 '20 at 08:12
If I change the date to 25/25/2020 your solution returns true. – Glyn Mar 01 '20 at 04:50
check with "2012-10-32" it will show date is valid but it is not a valid date. – dev verma Jul 28 '20 at 09:49
@Glyn after changing date, did you click `Run` button on Upper Left corner of the fiddle to reload the changes? – gschambial Jul 30 '20 at 09:58
@devverma Pl. check my comment above – gschambial Jul 30 '20 at 10:01
@BillalBegueradj Pl. check my comment – gschambial Jul 30 '20 at 10:02

score 19 · Answer 6 · edited Feb 26 '19 at 10:25

19

I use moment along with new Date to handle cases of undefined data values:

const date = moment(new Date("2016-10-19"));

because of: moment(undefined).isValid() == true

where as the better way: moment(new Date(undefined)).isValid() == false

edited Feb 26 '19 at 10:25

Moshe Slavin

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answered Jan 16 '19 at 23:18

wakeupoj

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moment(new Date('Decimal128')).isValid() // true – Predrag Stojadinović Jun 29 '23 at 11:39

score 8 · Answer 7 · answered May 21 '19 at 06:47

console.log(` moment('2019-09-01', 'YYYY-MM-DD').isValid()?  ` +moment('2019-09-01', 'YYYY-MM-DD').isValid())
console.log(` moment('2019-22-01', 'YYYY-DD-MM').isValid()?  ` +moment('2019-22-01', 'YYYY-DD-MM').isValid())
console.log(` moment('2019-22-22', 'YYYY-DD-MM').isValid()?  ` +moment('2019-22-22', 'YYYY-DD-MM').isValid())
console.log(` moment('undefined', 'YYYY-DD-MM').isValid()?  ` +moment('undefined', 'YYYY-DD-MM').isValid())

 moment('2019-09-01', 'YYYY-MM-DD').isValid()?  true
 moment('2019-22-01', 'YYYY-DD-MM').isValid()?  true
 moment('2019-22-22', 'YYYY-DD-MM').isValid()?  false
 moment('undefined', 'YYYY-DD-MM').isValid()?  false

could you please add some explanation to your answer? What additional value does this add to the already existing and accepted answer? — slfan, May 21 '19 at 07:08

score 6 · Answer 8 · answered Dec 11 '21 at 09:14

6

What I have used is moment.js

let value = '19-05-1994';
let check = moment(value,'DD-MM-YYYY', true).isValid();
        console.log(check) //returns true
        return check

answered Dec 11 '21 at 09:14

oluwatyson

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score 4 · Answer 9 · edited Jul 12 '20 at 09:18

4

If the date is valid then the getTime() will always be equal to itself.

var date = new Date('2019-12-12');
if(date.getTime() - date.getTime() === 0) {
    console.log('Date is valid');
} else {
    console.log('Date is invalid');
}

edited Jul 12 '20 at 09:18

General Grievance

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answered Jul 12 '20 at 04:31

Tanzeem Bhatti

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Erisan Olasheni · Answer 10 · 2021-08-27T09:08:00.000

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You can use

var d = moment("2016-10-19",dateFormat);
if(!isNaN(d)) {
  // d is a valid date.
}

edited Aug 27 '21 at 09:08

answered Aug 27 '21 at 07:59

Erisan Olasheni

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score 0 · Answer 11 · edited Oct 20 '22 at 06:50

0

moment("2022-10-18 04:00 AM", "YYYY-MM-DD HH:mm AM", true).isValid()

edited Oct 20 '22 at 06:50

starball

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answered Oct 19 '22 at 19:19

Ashish

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score -3 · Answer 12 · edited Jul 02 '18 at 17:07

-3

Try this one. It is not nice but it will work as long as the input is constant format from your date picker.

It is badDate coming from your picker in this example

https://jsfiddle.net/xs8tvox9/

var dateFormat = 'DD-MM-YYYY'
var badDate = "2016-10-19";

var splittedDate = badDate.split('-');

if (splittedDate.length == 3) {
  var d = moment(splittedDate[2]+"-"+splittedDate[1]+"-"+splittedDate[0], dateFormat);
  alert(d.isValid())
} else {
  //incorrectFormat
}

edited Jul 02 '18 at 17:07

Phil3992

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answered Oct 19 '16 at 06:57

Pochen

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Please, don't do this. – jeffci Jan 17 '20 at 15:29

Check if date is a valid one

12 Answers12

How to check if a string is a valid date using Moment, when the date and date format are different

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