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momentjsluxon

Luxon DateTime fromISO off by one hour versus moment.js

Trying to replace moment.js in my Angular application with Luxon to reduce bundle size.

I have come across a case where the two libraries produce a different output, and I am not sure why.

moment.js produces a date that is one hour ahead.

const activeToDateTimeString = '2014-08-06T13:07:04';

let foo1 = moment(activeToDateTimeString).utcOffset(-5, true);
let foo2 = DateTime.fromISO(activeToDateTimeString, {zone: 'America/New_York'}).setZone('America/New_York', { keepLocalTime: true });
let foo3 = DateTime.fromJSDate(new Date(activeToDateTimeString)).setZone('America/New_York', { keepLocalTime: true });
let foo4 = DateTime.fromISO(activeToDateTimeString).setZone('America/New_York', { keepLocalTime: true });

console.log(foo1.toDate());
console.log(foo2.toJSDate());
console.log(foo3.toJSDate());
console.log(foo4.toJSDate());

Output:

Wed Aug 06 2014 14:07:04 GMT-0400 (Eastern Daylight Time)
Wed Aug 06 2014 13:07:04 GMT-0400 (Eastern Daylight Time)
Wed Aug 06 2014 13:07:04 GMT-0400 (Eastern Daylight Time)
Wed Aug 06 2014 13:07:04 GMT-0400 (Eastern Daylight Time)

Why does moment.js produce a different output in this case?

Solution 
  • let foo1 = moment(activeToDateTimeString).utcOffset(-4, true);

    This would correct your code, but as you're moving to Luxon the daylight time changes won't effect you in the future.

    Right now (19 mar 2020) New York is 4 hours behind UTC as from the 8th March 2020 it entered Eastern Daylight Time from Eastern Standard Time.

    If New York was in Eastern Standard Time at the moment your code would output the same times.