Format Date-timeR←X(1200⌶)Y

Y is a numeric array of any shape, where every element contains a Dyalog Date Number that represents a date between 1 January 0001 and 31 December 9999 in the Proleptic Gregorian Calendar.

X is a character scalar or vector specifying a pattern with which the elements in Y should be formatted.

R is an array of the same shape as Y, whose elements are enclosed character vectors.

Formatting Pattern in `X`

The formatting pattern allows a time number to be converted to a highly user-configurable, plain text format. When a time number is formatted, elements in the result are copies of the format pattern with format sequences replaced by the elements they represent.

The format sequences are intended to be visually reminiscent of the generated text. They use alphabetic characters easily associated with the substitution (e.g. D, M and Y for Day, Month and Year respectively) repeated one or more times to indicate format. As noted below, some sequences allow the first character to be replaced by a _, or the casing to be altered.

letter	Length	Meaning	Variations	Example
Year	YY	Without century	YY	19
Year	YYYY	With century	YYYY	2019
Month	M	1 or 2 digit numeric	M	3
	MM	2 character numeric	MM _M	03 3
	MMM	Abbreviated name	MMM Mmm mmm _mm	MAR Mar mar Mar
	MMMM	Full name	MMMM Mmmm mmmm _mmm	MARCH March march March
Day of month	D	1 or 2 digit numeric	D	4
Day of month	DD	2 character numeric	DD _D	04 4
hours	h	1 or 2 digit numeric	h	8
hours	hh	2 character numeric	hh _h	08 8
minutes	m	1 or 2 digit numeric	m	5
minutes	mm	2 character numeric	mm _m	05 5
seconds	s	1 or 2 digit numeric	s	0
seconds	ss	2 character numeric	ss _s	00 0
fractional seconds	f	1 digit precision	f	5
	ff	2 digit precision	ff	55
	fff	3 digit precision	fff	555
	ffff	4 digit precision	ffff	5555
	fffff	5 digit precision	fffff	55555
	ffffff	6 digit precision	ffffff	555555
day of week	d	Numeric (1-7)	d	1
	ddd	Abbreviated name	DDD Ddd ddd _dd	MON Mon mon Mon
	dddd	Full name	DDDD Dddd dddd _ddd	MONDAY Monday monday Monday
ISO week number	w	1 or 2 digit numeric	w	10
ISO week number	ww	2 character numeric	ww _w	10 10
year of ISO Week number	WW	Without century	WW	19
year of ISO Week number	WWWW	With century	WWWW	2019
day of year	y	1 to 3 digit numeric	y	63
day of year	yy	3 character numeric	yy _y	063 63
Ordinal indicator for day of month	O	Short	O o	T t
Ordinal indicator for day of month	OO	Full	OO Oo oo	TH Th th
hours in twelve hour clock	t	1 or 2 digit numeric	t	8
hours in twelve hour clock	tt	2 character numeric	tt _t	08
AM/PM Indicator	P	Short	P p	A a
AM/PM Indicator	PP	Full	PP pp	AM am

The upper and lower case letters, underscore _, dollar $ and percent % are all reserved for introducing format sequences, even though not all currently have meaning. The remaining, non-reserved, characters are copied to the result unchanged, thus the format string hh:mm represents the hour of the day and minute of the hour with a colon between ( e.g. 12:00). All characters or sequences of characters may be delimited by " or ' at any point in the format string to prevent them being interpreted as a part of a format sequence, and, within these delimiters, two adjacent delimiter characters produce a single delimiter.

Note: The characters AaaaBbbb consist of two adjacent format sequences because there is a sequence of As followed by a sequence of Bs. The characters AaaaAaaa consist of one format sequence because it only contains As. It can be separated into two format sequences by insering an empty " or ' - delimited string, e.g. Aaaa""Aaaa.

Language

Unless overridden, English is used for text substitutions. Different languages may be selected using the Language variant option and/or the use of language specifiers within the format pattern. In either case, the language is specified as either a two letter ISO 639-1 language code in lower case (e.g. en) or as a five character language with an additional underscore and two character region in upper case (e.g. en_GB). Within the format pattern, xx (where xx is the two or five character specifier) will switch the language of the subsequent generated text. Dictionaries for the following languages are built in:

ISO 639-1	Language
da	Danish
de	German
el	Greek
en	English
es	Spanish
fi	Finnish
fr	French
it	Italian
ja	Japanese
nb	Norwegian Bokmål
nl	Dutch
nn	Norwegian Nynorsk
pl	Polish
pt	Portuguese
ru	Russian
sv	Swedish
zh	Chinese

Predefined patterns

Any pattern can contain (in part or in whole) a named predefined pattern, which allows common date and time formats to be specified in abbreviated form. Predefined patterns may be specified on a per-language basis, allowing patterns to be tailored for the selected language.

Predefined patterns are included in a pattern using % delimiters. For example, %ISO% includes the named predefined pattern ISO.

The following global predefined pattern is built in:

Name	Substitutes as
ISO	YYYY-MM-DD"T"hhss

This list may be expanded in future.

Additional predefined patterns may be defined using the Dictionary variant option. Predefined patterns must not contain references to other predefined patterns.

Variant Options

The Language variant option specifies the language used for formatting datetimes and defaults to 'en' (English). The option value is a two or five character name (e.g. 'en' or 'en_GB'). The setting may be explicitly overridden in the format pattern.

The Dictionary variant option specifies a namespace which contains additional or replacement names for the months etc. and/or predefined patterns, for languages and language regions.

At the top level there may be zero or more sub-namespaces with two or five character names, according to the rules for language and language regions. Within each of these, month names etc. are defined as follows:

Named item	Description
MonthNames	A twelve-element vector of character vectors containing the full names corresponding to January to December, respectively.
ShortMonthNames	A twelve-element vector of character vectors containing the short names corresponding to Jan to Dec, respectively.
WeekdayNames	A seven-element vector of character vectors containing the full names corresponding to Monday to Sunday, respectively.
ShortWeekdayNames	A seven-element vector of character vectors containing the full names corresponding to Mon to Sun, respectively.
MorningAfternoon	A two-element vector of character vectors containing the names corresponding to AM and PM, respectively.
Ordinals	A character vector containing the one ordinal used for all numbers in the range 1 to 31, or a thirty one-element vector of character vectors containing the ordinals for 1 to 31, respectively.

Also at the top level of the dictionary namespace there may be a sub-namespace named Patterns and within this further sub-namespaces named Global and/or two or five character language names, containing definitions of predefined patterns. Predefined patterns are defined in the same way as the formatting pattern except that they may not contain references to other predefined patterns.

If the namespace contains a definition which is supplied built into the interpreter, it replaces the built-in one.

If a dictionary is incomplete (e.g. is missing one of the expected named items, or one of the named items contains too few elements) an error is signalled only if the missing content would actually be needed.

Example dictionary

The following creates a dictionary defined by the namespace dict using JSON text. See the formatting examples below for uses of this dictionary.

      dict_json
{
  "Patterns": {
    "Global": {
      "ISOweek": "YYYY-'W'ww",
      "DateCompact": "D-MMM-YYYY",
      "DateVerbose": "'the date is' DD _mm YYYY"
    },
    "fr": {
      "DateVerbose": "'la date est le' DD mmm YYYY"
    },
    "en_US": {
      "DateVerbose": "'the date is' Mmm DD, YYYY"
    }
  },
  "en_US": {
    "ShortMonthNames": [
      "Jan.", "Feb.", "Mar.", "Apr.", "May", "June",
      "July", "Aug.", "Sept.", "Oct.", "Nov.", "Dec."
    ]
  },
  "cy": {
    "MonthNames": [
      "Ionawr", "Chwefror", "Mawrth", "Ebrill", "Mai", "Mehefin",
      "Gorffennaf", "Awst", "Medi", "Hydref", "Tachwedd", "Rhagfyr"
    ],
    "ShortMonthNames": [
      "Ion", "Chw", "Maw", "Ebr", "Mai", "Meh",
      "Gor", "Awst", "Medi", "Hyd", "Tach", "Rhag"
    ],
    "WeekdayNames": [
      "Dydd Sul", "Dydd Llun", "Dydd Mawrth", "Dydd Mercher",
      "Dydd Iau", "Dydd Gwener", "Dydd Sadwrn"
    ],
    "ShortWeekdayNames": [
      "Sul", "Llun", "Maw", "Mer", "Iau", "Gwen", "Sad"
    ],
    "MorningAfternoon": [
      "yb", "yh"
    ],
    "Ordinals": [
      "af", "il", "ydd", "ydd", "ed", "ed", "fed", "fed", "fed",
      "fed", "eg", "fed", "eg", "eg", "fed", "eg", "eg", "fed",
      "eg", "fed", "ain", "ain", "ain", "ain", "ain", "ain",
      "ain", "ain", "ain", "ain", "ain"
    ]
  }
}
      dict←⎕JSON dict_json

Note the following

In the example, the predefined pattern ISOweek is defined globally and is not redefined. It therefore has the same value for all languages. Similarly, DateCompact has the same value for all languages, but although the definition is global, it contains the pattern MMM and this will be substituted with the month name in the selected language.
The predefined patterns DateVerbose is defined globally, and redefined for languages fr and en_US. The global definition will be used when any language other than fr and en_US is selected. If there was not global definition it would only be defined for fr, all regional variations of fr, and en_US.
There is no explicit definition of patterns or names for language region en_GB. If this language is selected the definitions for en will be used.
There is an explicit definition for ShortMonthNames for language region en_US. If this language is selected the definition of ShortMonthNames is as defined, and as for en for other names. As en is not defined in the dictionary, the built-in defaults are used.

In the following examples:

      tn←1 ⎕DT ⊂2019 2 13 10 16 56
      tn
43508.42843

English

      'Dddd, DDoo Mmmm YYYY; hh:mm:ss' (1200⌶) tn
 Wednesday, 13th February 2019; 10:16:56

      '__en__Dddd, DDoo Mmmm YYYY; hh:mm:ss' (1200⌶) tn
 Wednesday, 13th February 2019; 10:16:56

      '"ISO date": %ISO%' (1200⌶) tn
 ISO date: 2019-02-13T10:16:56

      '%DateVerbose%'(1200⌶⍠'Dictionary'dict) tn
 the date is 13 Feb 2019

English (US)

     fmt←'%DateVerbose%'
     fmt (1200⌶⍠('Dictionary'dict)('Language' 'en_US'))tn
 the date is Feb. 13, 2019

Danish

      '__da__Dddd, DDoo mmmm YYYY; hh:mm:ss' (1200⌶) tn
 Onsdag, 13. februar 2019; 10:16:56

      fmt←'Dddd, DDoo mmmm YYYY; hh:mm:ss'
      fmt(1200⌶⍠'Language' 'da') tn
 Onsdag, 13. februar 2019; 10:16:56

Welsh (using the dictionary defined above)

      fmt←'__cy__Dddd, DDoo mmmm YYYY; hh:mm:ss' 
      fmt (1200⌶⍠'Dictionary' dict) tn
 Dydd Mercher, 13eg chwefror 2019; 10:16:56 


      '__cy__%DateVerbose%' (1200⌶⍠'Dictionary' dict) tn
 the date is 13 Chw 2019