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.

Twocolor

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? – Remittance

The input is coming from date picker. Can't change that too :( – Twocolor

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 – Remittance

really can't say. But that is not in my control to change that value. – Twocolor

Possible duplicate of How to test a string is valid date or not using moment? – Waxen

Answer 1

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.

Twocolor

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 github.com/moment/moment/issues/1407 for more info. – Salts

@Salts Please look at #23263880, github.com/moment/moment/issues/2535 – Twocolor

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.) – Irinairis

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. – Benevolent

need to add that moment('02').isValid() === true, so you might want to be careful with that – Fullmer

Also moment('abcde 1').isValid() === true – Swale

Warning: isValid() is not in any way reliable without a format. Do not be burnt – Megan

This is a wrong answer because I always get true whatever string I pass in – Tum

var date = moment("2016-10-32") this is not valid date but it is returning date is valid – Thickening

Also moment(undefined).isValid() === true (?) – Nosh

Answer 2

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.

Salts

This has no effect. – Tum

this answer should be the correct answer........@Begueradj this has effect, try using different values, sometimes correct and sometimes wrong – Hudgens

And you can read about strict parsing here – Ewer

This will let you enter 0000 as a year – Hemorrhoidectomy

Answer 3

I just found a really messed up case.

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

Phototransistor

moment('Decimal128', 'YYYY-MM-DD', true).isValid() // false. Use strict mode :) momentjs.com/guides/#/parsing/strict-mode – Hunkydory

Strict mode works. Weird that this has to be strict though. – Phototransistor

Answer 4

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.

Agreeable

if we pass true as 3rd argument for moment, it check's for exact date format. – Milker

Answer 5

Here you go: Working Fidddle

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

Devitrify

Like I said the dateFormat is 'DD-MM-YYYY' and I am not allowed to change it. – Twocolor

Oh i see. Let me see on that. – Devitrify

Is it allowed to change the date string here 2016-10-19? – Devitrify

Nope. That is coming from date picker – Twocolor

Can't you modify it after it comes from datepicker and before you input it to var d = moment("2016-10-19",dateFormat);? – Devitrify

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. – Twocolor

@Twocolor You don't have to modify dateFormat or dateString. – Devitrify

It outputs true but it should output false. Plus whatever I write, it gives random results – Tum

If I change the date to 25/25/2020 your solution returns true. – Underworld

check with "2012-10-32" it will show date is valid but it is not a valid date. – Thickening

@Underworld after changing date, did you click Run button on Upper Left corner of the fiddle to reload the changes? – Devitrify

@devverma Pl. check my comment above – Devitrify

@BillalBegueradj Pl. check my comment – Devitrify

Answer 6

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

Priority

moment(new Date('Decimal128')).isValid() // true – Conditioned

Answer 7

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

Puente

could you please add some explanation to your answer? What additional value does this add to the already existing and accepted answer? – Tropical

Answer 8

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

Amiamiable

Answer 9

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');
}

Licht

Answer 10

You can use

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

Larrup

Answer 11

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

Urbani

Answer 12

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
}

Remittance

Please, don't do this. – Igorot