Transform Tick to Date in JS

Question

I'm trying to check the expiration date of a JWT token and everything I tried is not getting me the right date.

"exp": 1522210228 => real answer => Wednesday, March 28, 2018 12:10:28 AM

I've tried thoses libs and I didn't get those to work...

1. https://github.com/auth0/angular2-jwt/blob/master/src/jwthelper.service.ts
2. https://github.com/auth0/jwt-decode

1

const helper = new JwtHelperService();
const decodedToken = helper.decodeToken(this.authentificationInfos.token);
const expirationDate = helper.getTokenExpirationDate(this.authentificationInfos.token);

console.log(expirationDate); => null?

2

import * as decode from 'jwt-decode';

const token = decode<{ data: { exp: number, iat: number, iss: string, nbf: number, username: string } }>(this.authentificationInfos.token);
const date = new Date(token.data.exp);
console.log(date); => Sun Jan 18 1970 09:50:10 GMT-0500 (Eastern Standard Time)

const d = new Date(0);
d.setUTCMilliseconds(token.data.exp);
console.log(d); => Sun Jan 18 1970 09:50:10 GMT-0500 (Eastern Standard Time)

Here is the complete token:

eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJkYXRhIjp7InVzZXJuYW1lIjoiYmlsb2RlYXV2aW5jZW50QG91dGxvb2suY29tIiwiaWF0IjoxNTIyMjA2NjI4LCJpc3MiOiJtbnAuY29tIiwibmJmIjoxNTIyMjA2NjI4LCJleHAiOjE1MjIyMTAyMjh9fQ.1WRlQatauXw2HEWj9B9VL6fIVR-4nAoKuWvkS4_m86k

https://jwt.io/ is decoding the token and the exp displayed is correct.

How can I get the real date from token.exp?

Answer 1

The timestamps in JWT are UNIX timestamps counting from 01.01.1970 00:00 UTC: https://www.rfc-editor.org/rfc/rfc7519#section-4.1.4 explains that a numeric date is used for the exp claim (and also for the nbf (not before) and iat (issued at) claims)

https://www.rfc-editor.org/rfc/rfc7519#section-2 defines the numeric date:

A JSON numeric value representing the number of seconds from 1970-01-01T00:00:00Z UTC until the specified UTC date/time, ignoring leap seconds.

var jwtDecode = require('jwt-decode');
var jwt = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJkYXRhIjp7InVzZXJuYW1lIjoiYmlsb2RlYXV2aW5jZW50QG91dGxvb2suY29tIiwiaWF0IjoxNTIyMjA2NjI4LCJpc3MiOiJtbnAuY29tIiwibmJmIjoxNTIyMjA2NjI4LCJleHAiOjE1MjIyMTAyMjh9fQ.1WRlQatauXw2HEWj9B9VL6fIVR-4nAoKuWvkS4_m86k";

const token = jwtDecode(jwt);
const d = new Date(0);
d.setUTCSeconds(token.data.exp);
console.log(d);

output:

2018-03-28T04:10:28.000Z

Use d.getHours(), d.getMinutes() etc. to get your local time.

Answer 2

Since it is a value of seconds from epoch, all you have to do is multiply exp by 1000.

See demo below.

const jwt = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IllvIiwiZXhwIjoxNTE2MjM5MDIyfQ.9xA3RWBjEdQmUFlf5E7fLrR8Xi36ogcjGrOdkL6DA3Y";

const decodedJwt = jwt_decode(jwt);

console.log( new Date(decodedJwt.exp * 1000) );

// output: "2018-01-18T01:30:22.000Z"

<script src="https://unpkg.com/[email protected]/build/jwt-decode.js"></script>

Answer 3

import jwt_decode from 'jwt-decode';

const token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IllvIiwiZXhwIjoxNTE2MjM5MDIyfQ.9xA3RWBjEdQmUFlf5E7fLrR8Xi36ogcjGrOdkL6DA3Y"
let _expData = jwt_decode(token || '{}')
let _exp = token.exp * 1000
let _date = new Date(_exp)
console.log(_date)