JavaScript Date.Utc() Function Is Off by a Month

Javascript Date.UTC() function is off by a month?

The month is zero-based for JavaScript.

Days and years are one-based.

Go figure.

UPDATE

The reason this is so, from the creator of JavaScript, is

JS had to "look like Java" only less so, be Java's dumb kid brother or boy-hostage sidekick. Plus, I had to be done in ten days or something worse than JS would have happened.

http://www.jwz.org/blog/2010/10/every-day-i-learn-something-new-and-stupid/#comment-1021

javascript UTC timestamp convert to Date 1 month off

Javascript months are zero based

This is a duplicate question

Check this thread for more insight Javascript Date.UTC() function is off by a month?

Date.UTC output is wrong

Month should be a number between 0 and 11, not 1 and 12. See the documentation

Is the Javascript date object always one day off?

Notice that Eastern Daylight Time is -4 hours and that the hours on the date you're getting back are 20.

20h + 4h = 24h

which is midnight of 2011-09-24. The date was parsed in UTC (GMT) because you provided a date-only string without any time zone indicator. If you had given a date/time string w/o an indicator instead (new Date("2011-09-24T00:00:00")), it would have been parsed in your local timezone. (Historically there have been inconsistencies there, not least because the spec changed more than once, but modern browsers should be okay; or you can always include a timezone indicator.)

You're getting the right date, you just never specified the correct time zone.

If you need to access the date values, you can use getUTCDate() or any of the other getUTC*() functions:

var d,
  days;
d = new Date('2011-09-24');
days = ['Sun', 'Mon', 'Tues', 'Wed', 'Thurs', 'Fri', 'Sat'];
console.log(days[d.getUTCDay()]);

What is the source of this off-by-one error in a JavaScript date?

Other than mixing UTC and local dates, the way you're adding 3 months will cause an incorrect response for dates like 31 March, where adding 3 months simply by incrementing the month number results in a date for 1 July. See Adding months to a Date in JavaScript.

So validate('07,2020') will return false if run on 31 March.

To fix that, when adding months, check that the updated date is still on the same day in the month, otherwise it's rolled over so set it to the last day of the previous month.

function validate(s) {  let testDate = addMonths(new Date(), 3);  let [m, y] = s.split(/\D/);  return testDate < new Date(y, m-1);};
function addMonths(date, months) {  let d = date.getDate();  date.setMonth(date.getMonth() + +months);  // If rolled over to next month, set to last day of previous month  if (date.getDate() != d) {    date.setDate(0);  }  return date;}
// Sampleconsole.log('On ' + new Date().toDateString() + ':');['07/2020', '04/2020'].forEach(  s => console.log(s + ' - ' + validate(s)));

Why Date.UTC(2015, 08, 31) == Date.UTC(2015, 09, 01) in javascript?

The month parameter is zero-indexed. So 8 is actually september which only has 30 days. So it flows over to october.

Reference: Date.UTC()

How to convert a Date to UTC?

The toISOString() method returns a string in simplified extended ISO
format (ISO 8601), which is always 24 or 27 characters long
(YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ,
respectively). The timezone is always zero UTC offset, as denoted by
the suffix "Z".

Source: MDN web docs

The format you need is created with the .toISOString() method. For older browsers (ie8 and under), which don't natively support this method, the shim can be found here:

This will give you the ability to do what you need:

var isoDateString = new Date().toISOString();
console.log(isoDateString);

Javascript date - month always increment

Javascript Date's month starts from 0. So 7 is actually 8th Month which is August.

month

Integer value representing the month, beginning with 0 for January to 11 for December.

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