Skip to content

LibreOffice date acceptance patterns

Update 2012-08-31T23:08+0200 : Editable Date Acceptance Patterns in LibreOffice

Abstract: Calc's (and in Writer table) cell input now needs to match locale dependent date acceptance patterns before it is recognized as a valid date.

Previously the number formatter's input scanner was very lax in what it accepted as a "valid" date. All combinations of 2-3 numbers separated by '.' '/' '-' or the locale's date separator even with blanks in between that somehow could be interpreted as a date was accepted as such, which was especially confusing with incomplete dates containing only 2 numbers that in many cases were meant as textual input instead. For example

  • In en-US locale, M/D is a valid date input to be interpreted as day of month of current year. However, M/D/ and M.D. were accepted as well.
  • In de-DE locale, D.M. is a valid date input to be interpreted as day of month of current year. However, D.M and D/M and D/M/ were accepted as well.

In case of an input like 1.2 in a de-DE locale or others using '.' separator, meant as some sort of textual numbering, this was extremely annoying, it was interpreted as 1st of February of current year and the user had to prepend a single quote / apostrophe to suppress date recognition. Similar for 1.2.3 in locales that do not use the '.' date separator.

Now, during build time for each locale one full date acceptance pattern is generated from the existing locale data's number format FormatElement with formatindex="21" that is also used to edit dates, taking the DMY order and the defined DateSeparator. For example, in the en-US locale this generates M/D/Y from the MM/DD/YYYY FormatCode, and in the de-DE locale D.M.Y from the DD.MM.YYYY code. For this to work correctly the separator used in the FormatCode must match the DateSeparator element defined in Separators. As for all rules there's one exception though ;) if the format code uses a different separator and that is one of the known '-' '.' '/' separators, a second pattern is generated using the format's separator. This as a generalized case for locales that for example may use an ISO 8601 edit format, as hu-HU does, regardless what the date separator is defined to.

Additionally to the date acceptance pattern every locale of course still accepts input in an ISO 8601 Y-M-D pattern, and since LibreOffice 3.5 that also leads to the YYYY-MM-DD format being applied.

Localizers, HEADS UP please

If in your locale incomplete dates should be accepted or additional patterns that vary from the generated full date pattern are needed, those are to be defined in the locale data LC_FORMAT element for which a new DateAcceptancePattern element exists, of which zero or more can occur before the FormatElement elements. Currently only the following patterns are defined as they are the only ones I knew were plausible:

  • bg-BG, a trailing breaking or non-breaking space followed by lower case or upper case Cyrillic letter GHE and a dot, as defined in the edit format
    • D.M.Y г.
    • D.M.Y г.
    • D.M.Y Г.
    • D.M.Y Г.
  • de-DE, incomplete date
    • D.M.
  • en-US, incomplete date
    • M/D
  • sl-SI, date separator dot plus space
    • D. M. Y

For example see i18npool/source/localedata/data/en_US.xml

Happy date accepting :-)

Update: an updated list of locales and patterns is available in a newer blog post.

LibreOffice possessive genitive case and partitive case month names

Poss...what? you may ask.. yes, the month that owns the day-of-month.

In some languages (and thus locales) a month name has different cases, depending on the context the name is used in. That's for example the case in Slavic languages, Greek, Russian, Finnish, Gaelic, ... and probably a few more I didn't hear of. Totally unknown to native English speakers ;-) (which I'm not)

  • a standalone month name is the nominative case, the noun, as in November
  • a possessive genitive case month name can be described as "the month's day", as in November's 17th
  • a partitive case month name can be described as "day of month", as in 17 of November

This feature in number formatting was requested for quite some time. Recently I found time to implement it. To achieve this, I added optional elements to LibreOffice's internal locale data <LC_CALENDAR><Calendar> element and implemented the general rules in the number formatter.

Locale data (submitted by localizers)
  • <MonthsOfYear> element, nominative (nouns) month names
    • always specified
    • includes <Month>, <MonthID>, <DefaultAbbrvName> and <DefautFullName> elements
  • <GenitiveMonths> element, genitive case month names
    • optional
    • follows the <MonthsOfYear> element
    • consists of same elements as <MonthsOfYear> element
    • if <GenitiveMonths> are not specified then <MonthsOfYear> names are used in the context of the number formatter's genitive case
  • <PartitiveMonths> element, partitive case month names
    • optional
    • follows the <GenitiveMonths> element, or follows the <MonthsOfYear> element if the <GenitiveMonths> element is not specified
    • consists of same elements as <MonthsOfYear> element
    • if <PartitiveMonths> are not specified then <GenitiveMonths> names are used, if that is not specified then <MonthsOfYear> names are used

Rules for use of nominative / genitive / partitive case month names in number formatter when encountering MMM or MMMM
  • MMM or MMMM immediately preceded or followed by a literal character other than space ⇒ nominative month name (noun), for Excel and backwards compatibility such as Finnish MMMM"ta"
  • no day of month (D or DD) present in format code ⇒ nominative name
  • day of month (D or DD) after MMM or MMMM ⇒ genitive name
    • no genitive names defined ⇒ nominative names
  • day of month (D or DD) before MMM or MMMM ⇒ partitive name
    • no partitive names defined ⇒ genitive names
      • no genitive names defined ⇒ nominative names

If only <MonthsOfYear> and <PartitiveMonths> are specified but not <GenitiveMonths>, then for MMM(M) D(D) formats the <MonthsOfYear> nominative name is displayed. Only for D(D) MMM(M) formats the <PartitiveMonths> name is displayed.

If only for MMM(M) D(D) formats the <GenitiveMonths> are to be displayed but nominative names for D(D) MMM(M), then specify <PartitiveMonths> identical to <MonthsOfYear>, do not omit it as otherwise it would inherit from <GenitiveMonths> again.


To illustrate, here's a screenshot using the Finnish fi-FI locale, Finnish is an extraordinary case that uses all three, nominative, genitive and partitive case month names.

Screenshot of nominative, genitive and partitive month names in Finnish.
Screenshot of nominative, genitive and partitive month names in Finnish.
Locales featuring month name cases
Currently for the following locales genitive and/or partitive case month names were contributed:
  • [an-ES] Aragonese, Spain
  • [ast-ES] Asturian, Spain
  • [be-BY] Belarusian, Belarus
  • [fi-FI] Finnish, Finland
  • [gd-GB] Gaelic (Scottish), United Kingdom
  • [la-VA] Latin, State of the Vatican City
  • [lt-LT] Lithuanian, Lithuania
  • [ru-RU] Russian, Russia

As you can see, that's only a few locales and not all that should be covered. So if you're working on localization of LibreOffice and your language uses month name cases, please contribute the locale data additions as lined out above. Best send a patch of your locale's .xml data file as attachment to the developer mailing list and I'll pick it up. If uncertain how to do that just ask and we'll help. For an example how the data looks like see i18npool/source/localedata/data/lt_LT.xml and search for GenitiveMonths. If you're interested in technical details of locale data files see i18npool/source/localedata/data/locale.dtd

Happy month casing :-)