# Formatting

This section covers creating strings to represent a DateTime. There are three types of formatting capabilities:

1. Technical formats like ISO 8601 and RFC 2822
2. Internationalizable human-readable formats
3. Token-based formatting

## Technical formats (strings for computers)

### ISO 8601

ISO 8601 is the most widely used set of string formats for dates and times. Luxon can parse a wide range of them, but provides direct support for formatting only a few of them:

    dt.toISO();         //=> '2017-04-20T11:32:00.000-04:00'
    dt.toISODate();     //=> '2017-W17-7'
    dt.toISOWeekDate(); //=> '2017-04-20'
    dt.toISOTime();     //=> '11:32:00.000-04:00'

Generally, you'll want the first one. Use it by default when building or interacting with APIs, communicating times over a wire, etc.

### HTTP and RFC 2822

There are a number of legacy standard date and time formats out there, and Luxon supports some of them. You shouldn't use them unless you have a specific reason to.

    dt.toRFC2822(); //=> 'Thu, 20 Apr 2017 11:32:00 -0400'
    dt.toHTTP();    //=> 'Thu, 20 Apr 2017 03:32:00 GMT'

## toLocaleString (strings for humans)

### The basics

Modern browsers (and other JS environments) provide brought support for human-readable, internationalized strings. Luxon provides convenient support for them, and you should use them anytime you want to display a time to a user. Use toLocaleString to do it:

    dt.toLocaleString();                                       //=> '4/20/2017'
    dt.toLocaleString(DateTime.DATETIME_FULL);                 //=> 'April 20, 2017, 11:32 AM EDT'
    dt.setLocale('fr').toLocaleString(DateTime.DATETIME_FULL); //=> '20 avril 2017 à 11:32 UTC−4'

### Intl.DateTimeFormat

In the example above, `DateTime.DATETIME_FULL` is one of several convenience formats provided by Luxon. But the arguments are really any object of options that can be provided to Intl.DateTimeFormat. For example:

    dt.toLocaleString({ month: 'long', day: 'numeric' }) //=> 'April 20'

And that's all the preset is:

    DateTime.DATETIME_FULL;  //=> {
                             //     year: 'numeric',
                             //     month: 'long',
                             //     day: 'numeric',
                             //     hour: 'numeric',
                             //     minute: '2-digit',
                             //     timeZoneName: 'short'
                             //   }

This also means you can modify the presets as you choose:

    dt.toLocaleString(DateTime.DATE_SHORT); //=>  '4/20/2017'
    var newFormat = Object.assign({ weekday: 'long' }, DateTime.DATE_SHORT);
    dt.toLocaleString(newFormat); //=>  'Thursday, 4/20/2017'

### Presets

Here's the full set of provided presets using the October 14, 1983 at 13:30:23 as an example.

Name | Description | Example in EN_US | Example in FR
--- | --- | --- | ---
DATE_SHORT | short date | 10/14/1983 | 14/10/1983
DATE_MED | abbreviated date | Oct 14, 1983 | 14 oct. 1983
DATE_FULL | full date | October 14, 1983 | 14 octobre 1983
DATE_HUGE | full date with weekday | Tuesday, October 14, 1983 | vendredi 14 octobre 1983
TIME_SIMPLE | time | 1:30 PM | 13:30
TIME_WITH_SECONDS | time with seconds | 1:30:23 PM | 13:30:23
TIME_WITH_SHORT_OFFSET | time with seconds and abbreviated named offset | 1:30:23 PM EDT | 13:30:23 UTC−4
TIME_WITH_LONG_OFFSET | time with seconds and full named offset | 1:30:23 PM Eastern Daylight Time | 13:30:23 heure d’été de l’Est
TIME_24_SIMPLE | 24-hour time | 13:30 | 13:30
TIME_24_WITH_SECONDS | 24-hour time with seconds | 13:30:23 | 13:30:23
TIME_24_WITH_SHORT_OFFSET | 24-hour time with seconds and abbreviated named offset | 13:30:23 EDT | 13:30:23 UTC−4
TIME_24_WITH_LONG_OFFSET | 24-hour time with seconds and full named offset | 13:30:23 Eastern Daylight Time | 13:30:23 heure d’été de l’Est
DATETIME_SHORT | short date & time | 10/14/1983, 1:30 PM | 14/10/1983 à 13:30
DATETIME_MED | abbreviated date & time | Oct 14, 1983, 1:30 PM | 14 oct. 1983 à 13:30
DATETIME_FULL | full date and time with abbreviated named offset | 14 octobre 1983 à 13:30 UTC−4 | 14 octobre 1983 à 13:30 UTC−4
DATETIME_HUGE | full date and time with weekday and full named offset | Friday, October 14, 1983, 1:30 PM Eastern Daylight Time | vendredi 14 octobre 1983 à 13:30 heure d’été de l’Est
DATETIME_SHORT_WITH_SECONDS | short date & time with seconds | 10/14/1983, 1:30:23 PM | 14/10/1983 à 13:30:23
DATETIME_MED_WITH_SECONDS | abbreviated date & time with seconds | Oct 14, 1983, 1:30:23 PM | 14 oct. 1983 à 13:30:23
DATETIME_FULL_WITH_SECONDS | full date and time with abbreviated named offset with seconds | October 14, 1983, 1:30:23 PM EDT | 14 octobre 1983 à 13:30:23 UTC−4
DATETIME_HUGE_WITH_SECONDS | full date and time with weekday and full named offset with seconds | Friday, October 14, 1983, 1:30:23 PM Eastern Daylight Time | vendredi 14 octobre 1983 à 13:30:23 heure d’été de l’Est

### Intl

`toLocaleString`'s behavior is affected by the DateTime's `locale`, `numberingSystem`, and `outputCalendar` properties. See the Intl section for more.

## Formatting with tokens (strings for Cthulhu)

This section covers generating strings from DateTimes with programmer-specified formats.

### Consider alternatives

You shouldn't create ad-hoc string formats if you can avoid it. If you intend for a computer to read the string, prefer ISO 8601. If a human will read it, prefer `toLocaleString`. Both are covered above. However, if you have some esoteric need where you need some specific format (e.g. because some other software expects it), then `toFormat` is how you do it.

### toFormat

See DateTime#toFormat for the API signature. As a brief motivating example:

    DateTime.fromISO('2014-08-06T13:07:04.054').toFormat('yyyy LLL dd') //=> '2014 Aug 06'

The supported tokens are described in the table below.

### Intl

All of the strings (e.g. month names and weekday names) are internationalized by introspecting strings generated by the Intl API. Thus they exact strings you get are implementation-specific.

    DateTime.fromISO('2014-08-06T13:07:04.054').setLocale('fr').toFormat('yyyy LLL dd') //=> '2014 août 06'

### Escaping

You may escape strings using single quotes:

    DateTime.local().toFormat("HH 'hours and' mm 'minutes'") //=> '20 hours and 55 minutes'

### Standalone vs format tokens

Some tokens have a "standalone" and "format" version. Some languages require different forms of a word based on whether it is part of a longer phrase or just by itself (e.g. "Monday the 22nd" vs "Monday"). Use them accordingly.

    var d = DateTime.fromISO('2014-08-06T13:07:04.054').setLocale('ru');
    d.toFormat("LLLL") //=> 'август' (format)
    d.toFormat("MMMM"); //=> 'августа' (standalone)

### Macro tokens

Some of the formats are "macros", meaning they correspond to multiple components. These use the native Intl API and will order their constituent parts in a locale-friendly way.

    DateTime.fromISO('2014-08-06T13:07:04.054').toFormat('ff') //=> 'Aug 6, 2014, 1:07 PM'

The macro options available correspond one-to-one with the preset formats defined for `toLocaleString`.

### Table of tokens

(Examples below given for 2014-08-06T13:07:04.054 considered as a local time in America/New_York).

Standlone token | Format token | Description | Example
--- | --- | --- | ---
S |  | millisecond, no padding | 54
SSS |  | millisecond, padded to 3 | 054
s |  | second, no padding | 4
ss |  | second, padded to 2 padding | 04
m |  | minute, no padding | 7
mm |  | minute, padded to 2 | 07
h |  | hour in 12-hour time, no padding | 1
hh |  | hour in 12-hour time, padded to 2 | 01
H |  | hour in 24-hour time, padded to 2 | 9
HH |  | hour in 24-hour time, padded to 2 | 13
Z |  | narrow offset | +5
ZZ |  | short offset | +05:00
ZZZ |  | techie offset | +0500
ZZZZ |  | abbreviated named offset | EST
ZZZZZ |  | unabbreviated named offset | Eastern Standard Time
z |  | IANA zone | America/New_York
a |  | meridiem | AM
d |  | day of the month, no padding | 6
dd |  | day of the month, padded to 2 | 06
c | E | day of the week, as number from 1-7 (Monday is 1, Sunday is 7) | 3
ccc | EEE | day of the week, as an abbreviate localized string | Wed
cccc | EEEE | day of the week, as an unabbreviated localized string | Wednesday
ccccc | EEEEE | day of the week, as a single localized letter | W
L | M | month as an unpadded number | 8
LL | MM | month as an padded number | 08
LLL | MMM | month as an abbreviated localized string | Aug
LLLL | MMMM | month as an unabbreviated localized string | August
LLLLL | MMMMM | month as a single localized letter | A
y |  | year, unpadded | 2014
yy |  | two-digit year | 14
yyyy |  | four-digit year | 2014
G |  | abbreviated localized era | AD
GG |  | unabbreviated localized era | Anno Domini
GGGGG |  | one-letter localized era | A
kk |  | ISO week year, unpadded | 17
kkkk |  | ISO week year, padded to 4 | 2014
W |  | ISO week number, unpadded | 32
WW |  | ISO week number, padded to 2 | 32
o |  | ordinal (day of year), unpadded | 218
ooo |  | ordinal (day of year), padded to 3 | 218
D |  | localized numeric date | 9/4/2017
DD |  | localized date with abbreviated month | Aug 6, 2014
DDD |  | localized date with full month | August 6, 2014
DDDD |  | localized date with full month and weekday | Wednesday, August 6, 2014
t |  | localized time | 9:07 AM
tt |  | localized time with seconds | 1:07:04 PM
ttt |  | localized time with seconds and abbreviated offset | 1:07:04 PM EDT
tttt |  | localized time with seconds and full offset | 1:07:04 PM Eastern Daylight Time
T |  | localized 24-hour time | 13:07
TT |  | localized 24-hour time with seconds | 13:07:04
TTT |  | localized 24-hour time with seconds and abbreviated offset | 13:07:04 EDT
TTTT |  | localized 24-hour time with seconds and full offset | 13:07:04 Eastern Daylight Time
f |  | short localized date and time | 8/6/2014, 1:07 PM
ff |  | less short localized date and time | Aug 6, 2014, 1:07 PM
fff |  | verbose localized date and time | August 6, 2014, 1:07 PM EDT
ffff |  | extra verbose localized date and time | Wednesday, August 6, 2014, 1:07 PM Eastern Daylight Time
F |  | short localized date and time with seconds | 8/6/2014, 1:07:04 PM
FF |  | less short localized date and time with seconds | Aug 6, 2014, 1:07:04 PM
FFF |  | verbose localized date and time with seconds | August 6, 2014, 1:07:04 PM EDT
FFFF |  | extra verbose localized date and time with seconds | Wednesday, August 6, 2014, 1:07:04 PM Eastern Daylight Time