For Moment users

Luxon borrows lots of ideas from Moment.js, but there are a lot of differences too. This document clarifies what they are.

Immutability

Luxon's objects are immutable, whereas Moment's are mutable. For example, in Moment:

var m1 = moment();
var m2 = m1.add(1, 'hours');
m1.valueOf() === m2.valueOf(); //=> true

This happens because m1 and m2 are really the same object; add() mutated the object to be an hour later. Compare that to Luxon:

var d1 = DateTime.now();
var d2 = d1.plus({ hours: 1 });
d1.valueOf() === d2.valueOf(); //=> false

This happens because the plus method returns a new instance, leaving d1 unmodified. It also means that Luxon doesn't require copy constructors or clone methods.

Major functional differences

1. Months in Luxon are 1-indexed instead of 0-indexed like in Moment and the native Date type.
2. Localizations and time zones are implemented by the native Intl API (or a polyfill of it), instead of by the library itself.
3. Luxon has both a Duration type and an Interval type. The Interval type is like Twix.

Other API style differences

1. Luxon methods often take option objects as their last parameter
2. Luxon has different static methods for object creation (e.g. fromISO), as opposed to Moment's one function that dispatches based on the input
3. Luxon parsers are very strict, whereas Moment's are more lenient.
4. Luxon uses getters instead of accessor methods, so dateTime.year instead of dateTime.year()
5. Luxon centralizes its "setters", like dateTime.set({year: 2016, month: 4}) instead of dateTime.year(2016).month(4) like in Moment.
6. Luxon's Durations are a separate top-level class.
7. Arguments to Luxon's methods are not automatically coerced into Luxon instances. E.g. m.diff('2017-04-01') would be dt.diff(DateTime.fromISO('2017-04-01')).

DateTime method equivalence

Here's a rough mapping of DateTime methods in Moment to ones in Luxon. I haven't comprehensively documented stuff that's in Luxon but not in Moment, just a few odds and ends that seemed obvious for inclusion; there are more. I've probably missed a few things too.

Creation

Getters and setters

Basic information getters

Unit getters

Programmatic get and set

For programmatic getting and setting, Luxon and Moment are very similar here:

Transformation

Query

Output

Basics

See the formatting guide for more about the string-outputting methods.

Humanization

Luxon has toRelative and toRelativeCalendar. For internationalization, they use Intl.RelativeTimeFormat (or fall back to English when it is not supported by the browser).

Durations

Moment Durations and Luxon Durations are broadly similar in purpose and capabilities. The main differences are:

1. Luxon durations have more sophisticated conversion capabilities. They can convert from one set of units to another using shiftTo. They can also be configured to use different unit conversions. See Duration Math for more.
2. Luxon does not (yet) have an equivalent of Moment's Duration humanize method. Luxon will add that when Intl.UnitFormat is supported by browsers.
3. Like DateTimes, Luxon Durations have separate methods for creating objects from different sources.

See the Duration API docs for more.

Intervals

Moment doesn't have direct support intervals, which must be provided by plugins like Twix or moment-range. Luxon's Intervals have similar capabilities to theirs, with the exception of the humanization features. See the Interval API docs for more.